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Long Term Effects of RV Pacing Tehran Arrhythmia Center April 2006.

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1 Long Term Effects of RV Pacing Tehran Arrhythmia Center April 2006

2 To Pace or not to Pace? Pacing the right ventricle

3 Deleterious Effects of RV Apical Pacing Altered left ventricular electrical and mechanical activation Altered left ventricular electrical and mechanical activation Altered ventricular function Altered ventricular function Less work produced for given LVEDV Less work produced for given LVEDV Delayed papillary muscle activation  Valvular insufficiency Delayed papillary muscle activation  Valvular insufficiency Remodeling Remodeling Modified regional blood flow patterns Modified regional blood flow patterns Increased oxygen consumption without increase in blood flow Increased oxygen consumption without increase in blood flow 60% change in blood flow between early and later activated regions 60% change in blood flow between early and later activated regions Abnormal thickening of LV wall Abnormal thickening of LV wall Cellular disarray Cellular disarray Fibrosis (away from pacing lead location) Fibrosis (away from pacing lead location) Fat deposition Fat deposition Calcification Calcification Mitochondrial abnormalities Mitochondrial abnormalities

4 Altered left ventricular mechanical activation Potential detrimental effect of RV apical pacing in the form of pacing-induced LV dyssynchrony secondary to the abnormal activation sequence Potential detrimental effect of RV apical pacing in the form of pacing-induced LV dyssynchrony secondary to the abnormal activation sequence Pacing-induced abnormalities of myocardial blood flow Pacing-induced abnormalities of myocardial blood flow RV apical pacing alters LV papillary muscle function, changing the timing sequence of the mitral valve apparatus, thus causing RV apical pacing alters LV papillary muscle function, changing the timing sequence of the mitral valve apparatus, thus causing MR.

5 Altered LV Electrical Activation Pattern Two break-out locations on LV endocardium Two break-out locations on LV endocardium Inferior border of the mid-septum Superior basal aspect of free wall Latest activation Latest activation Base of the inferior posterior wall Muscular conduction (less Purkinje fiber density) Muscular conduction (less Purkinje fiber density) Cassidy DM, et al. Circ 1984;70:37-42 Single break-out location on LV endocardium Single break-out location on LV endocardium Similar to left bundle branch block Latest activation Latest activation Similar to intrinsic Inferioposterior base Inferioposterior base Vassallo JA, et al. JACC 1986;7: Normal Sinus Rhythm Right Ventricular Apical Pacing

6 Apical Pacing Histopathology Karpawich (1990) – Pediatric Canine Model Karpawich (1990) – Pediatric Canine Model LV myofibril disarray was found after 4 months of pacing from RV apex LV myofibril disarray was found after 4 months of pacing from RV apex 90 degree misalignment of adjacent fibers (stress related?) 90 degree misalignment of adjacent fibers (stress related?) Also noted appearance of prominent Purkinje cells in subendocardium, variable-sized mitochondria, and dystrophic calcification Also noted appearance of prominent Purkinje cells in subendocardium, variable-sized mitochondria, and dystrophic calcification Karpawich (1999) – Pediatric Patients Karpawich (1999) – Pediatric Patients Myofibril hypertrophy, intracellular vacuolation, degenerative fibrosis, and fatty deposits in the LV after more than 3 years RV apical pacing Myofibril hypertrophy, intracellular vacuolation, degenerative fibrosis, and fatty deposits in the LV after more than 3 years RV apical pacing Independent of paced time, patient age, epi- or endocardial electrode placement, and mode Independent of paced time, patient age, epi- or endocardial electrode placement, and mode Adomain (1986) Adomain (1986) Myofibril disarray was found in 75% of canine hearts after 3 months of pacing from RV apex Myofibril disarray was found in 75% of canine hearts after 3 months of pacing from RV apex Greatest at base of left ventricular free wall Greatest at base of left ventricular free wall 25X: Karpawich PP, et al. Am Heart J 1990;119:

7 Clinical Studies of Adverse Effects of RV Pacing Pace,Vol.29, March 2006

8 Clinical Studies of Adverse Effects of RV Pacing Heart Rhythm, Vol 2, No 2, January 2005

9 Danish Study Overview Hypothesis: Hypothesis: In patients with SND, atrial pacing (AAI) will result in less atrial fibrillation, thromboembolism, heart failure and overall mortality than ventricular pacing (VVI). Study Design : Study Design : Single center, prospective, randomization of patients referred for first pacemaker implant

10 Primary: Primary: - Mortality - Cardiovascular death - Cardiovascular death Secondary: Secondary: -Atrial fibrillation -Thromboembolic events -Heart failure -AV block Danish Study Endpoints

11 Danish Study Patient Characteristics AAl GroupVVI Group No. of Patients Age, y Women7369 Men3746 Sinus bradycardia 1818 Sino atrial block 4946 Brady-Tachy Syndrome 4351

12 Danish Study Patient Characteristics AAl GroupVVI Group NYHA Class I7992 NYHA Class II2420 NYHA Class III73 NYHA Class IV00 Digoxin2211* Beta Blocker71 Calcium Blocker1311 Antiarrhythmic drugs126 Furosemide, mg/d Aspirin4846 Warfarin61 * P = 0.04, atrial versus ventricular group

13 Danish Study Overall survival by pacing mode Andersen H, et al. Lancet 1997; 350: p = Atrial pacing Ventricular pacing Time (years) Number of patients at risk during follow-up Atrial Ventricular

14 Danish Study Cardiovascular death by pacing mode Andersen H, et al. Lancet 1997; 350: Time (years) p = Atrial pacing Ventricular pacing Cumulative survival Number of patients at risk during follow-up Atrial Ventricular

15 Danish Study Cumulative risk of PAF by pacing mode Andersen H, et al. Lancet 1997; 350: p = Atrial pacing Ventricular pacing Time (years) Proportion without AF Number of patients at risk during follow-up Atrial Ventricular

16 Danish Study Cumulative risk of chronic AF by pacing mode Andersen H, et al. Lancet 1997; 350: p = Atrial pacing Ventricular pacing Time (years) Proportion without chronic AF Number of patients at risk during follow-up Atrial pacing Ventricular pacing

17 Danish Study Mortality as a result of CHF Andersen H, et al. Lancet 1997; 350: ,00,80, Atrial pacing Ventricular pacing p = 0.18 Time (years) Survival without death from CHF AAI: VVI:

18 Danish Study CHF Analysis NYHA classification was higher in the ventricular group vs. the atrial group (p=0.010) at long term follow up. NYHA classification was higher in the ventricular group vs. the atrial group (p=0.010) at long term follow up. During follow up, NYHA class worsened in the ventricular group vs. the atrial group (p<0.005) During follow up, NYHA class worsened in the ventricular group vs. the atrial group (p<0.005) Mean dose of diuretics increased in the ventricular group vs. the atrial group (p=0.033) Mean dose of diuretics increased in the ventricular group vs. the atrial group (p=0.033)

19 Danish Study Conclusions In patients with SND, atrial pacing is associated with a significantly higher survival, less atrial fibrillation, fewer thromboembolic complications, and less heart failure compared to ventricular pacing. In patients with SND, atrial pacing is associated with a significantly higher survival, less atrial fibrillation, fewer thromboembolic complications, and less heart failure compared to ventricular pacing.

20 Canadian Trial of Physiologic Pacing CTOPP

21 CTOPP Study Overview Hypothesis: Hypothesis: -Physiologic (DDDR or AAIR) pacing is superior to single-chamber (VVIR) pacing because it is associated with lower risks of atrial fibrillation, stroke, and death. Study Design: Study Design: -32 Canadian centers -Prospective, randomized

22 CTOPP Study Endpoints Primary: Primary: -Stroke or death due to cardiovascular causes Secondary: Secondary: -Death from any cause -Atrial fibrillation -Hospitalization for heart failure

23 CTOPP Study Protocol Patients undergoing first IPG implant n=2,568 Ventricular-Based Pacing n = 1,474 Physiologic Pacing n = 1,094 Follow for an average of 3 years and compare: Stroke or death due to cardiovascular causes Death from any cause Atrial fibrillation Hospitalization for HF

24 CTOPP Cumulative Risk of Stroke or Cardiovascular Death Cumulative Risk Years after Randomization P = 0.33 Ventricular pacing Physiologic pacing Connolly S et al. N Engl J Med 2000; 342: No. at risk: Ventricular pacing Physiologic pacing

25 CTOPP Cumulative Risk of any AF Cumulative Risk Years after Randomization P = 0.05 Ventricular pacing Physiologic pacing Connolly S et al. N Engl J Med 2000; 342: No. at risk: Ventricular pacing Physiologic pacing

26 CTOPP Cumulative Risk of Chronic AF Skanes A, et al. J Am Coll Cardiol 2001; 38: Cumulative Risk Years Since Randomization Number V At Risk P P = Ventricular pacing Physiologic pacing

27 CTOPP Conclusions Physiologic pacing (dual-chamber or atrial) provides little benefit over ventricular pacing for the prevention of stroke or death due to cardiovascular causes. Physiologic pacing (dual-chamber or atrial) provides little benefit over ventricular pacing for the prevention of stroke or death due to cardiovascular causes. Physiologic pacing does provide a reduction in the relative risk of paroxysmal and persistent AF. Physiologic pacing does provide a reduction in the relative risk of paroxysmal and persistent AF.

28 A Mode Selection Trial MOST Sub-Study Effect of Pacing Mode and Cumulative Percent Time Ventricular Paced on Heart Failure and Atrial Fibrillation in Patients with Sinus Node Dysfunction and Baseline QRS Duration <120 Milliseconds in MOST Michael O. Sweeney, Anne S. Hellkamp, Arnold J. Greenspon, Robert Mittleman, John McAnulty, Kenneth Ellenbogen, Roger Freedman, Kerry L. Lee, Gervasio A. Lamas, for the MOST Investigators Circulation 2003, in press

29 MOST Sub-Study Background: DDDR pacing preserves AV synchrony and reduces CHF compared to VVIR pacing in SND. DDDR pacing preserves AV synchrony and reduces CHF compared to VVIR pacing in SND. DDDR pacing results in prolonged QRS durations (QRSd) due to ventricular desynchronization. DDDR pacing results in prolonged QRS durations (QRSd) due to ventricular desynchronization.Hypothesis: DDDR pacing often results in prolonged QRS duration (QRSd) due to ventricular desynchronization in patients with normal baseline QRSd and may increase risk of heart failure and atrial fibrillation. DDDR pacing often results in prolonged QRS duration (QRSd) due to ventricular desynchronization in patients with normal baseline QRSd and may increase risk of heart failure and atrial fibrillation. Sweeney MO, et al. Circulation 2003, in press

30 Methods: Baseline QRSd obtained from 12-lead EKG prior to IPG implant in MOST (a 2,010 patient, 6-year randomized trial of DDDR vs. VVIR pacing in SND). Baseline QRSd obtained from 12-lead EKG prior to IPG implant in MOST (a 2,010 patient, 6-year randomized trial of DDDR vs. VVIR pacing in SND). Cumulative % time ventricular paced was determined from stored pacemaker diagnostic data. Cumulative % time ventricular paced was determined from stored pacemaker diagnostic data. Baseline QRSd <120 ms was observed in 1332 patients; 702 were randomized to DDDR; 640 to VVIR. Baseline QRSd <120 ms was observed in 1332 patients; 702 were randomized to DDDR; 640 to VVIR. MOST Sub-Study Sweeney MO, et al. Circulation 2003, in press

31 MOST Sub-Study: Results Cum%VP was greater in DDDR (90%) vs. VVIR (51%). Cum%VP was greater in DDDR (90%) vs. VVIR (51%). The rates of CHF hospitalization increased with Cum%VP: The rates of CHF hospitalization increased with Cum%VP: Sweeney MO, et al. Circulation 2003, in press

32 MOST Sub-study: Risk of HFH Relative to a DDDR Patient with Cum % VP = 0 Risk of HFH increased between 0% and 40% Cum VP, but was level at Cum%VP above 40%. Risk can be reduced to about 2% if ventricular pacing is minimized.

33 Sweeney MO, et al. Circulation 2003, in press MOST Sub-Study: Risk of HFH Relative to a VVIR Patient with Cum % VP = 0 Risk of CHF was constant between 0% and 80% Cum VP and increased by as much as 2.5-fold when Cum%VP exceeded 80%. Risk cannot be reduced regardless of minimization of ventricular pacing.

34 P=0.047 Sweeney MO, et al. Circulation 2003, in press MOST Sub-Study

35 P= Sweeney MO, et al. Circulation 2003, in press MOST Sub-Study

36 Higher rates of CHF hospitalization were associated with higher Cum% VP: Higher rates of CHF hospitalization were associated with higher Cum% VP: - - Cum % VP<10% was associated with the lowest rates of CHF hospitalization (DDDR 2%, VVIR 7%). - Cum % VP >90% was associated with the highest rates of CHF hospitalization (DDDR 12%, VVIR 16%). Ventricular pacing in the DDDR mode more than 40% confers a 3-fold increased risk of heart failure hospitalization but can be reduced to about 2% if ventricular pacing is minimized. Ventricular pacing in the DDDR mode more than 40% confers a 3-fold increased risk of heart failure hospitalization but can be reduced to about 2% if ventricular pacing is minimized. Sweeney MO, et al. Circulation 2003, in press MOST Sub-study Conclusions: CHF

37 Sweeney MO, et al. Circulation 2003, in press Risk of AF increases linearly with Cum%VP up to  % in both DDDR and VVIR MOST Sub-study: AF Risk

38 Sweeney MO, et al. Circulation 2003, in press MOST Sub-study: AF Risk

39 Sweeney MO, et al. Circulation 2003, in press MOST Sub-study: AF Risk

40 Relationship between risk of AF and Cum%VP was similar between pacing modes:Relationship between risk of AF and Cum%VP was similar between pacing modes: – –Risk of AF showed a linearly increasing relationship with increased Cum%VP from 0% pacing up to % pacing in both pacing modes. – –Within this range, the risk of AF increased by 1% for each 1% increase in Cum%VP (DDDR hazard ratio 1.01 [1.004, 1.022] p=0.012; VVIR 1.01 [1.001, 1.01], p=0.025). Sweeney MO, et al. Circulation 2003, in press MOST Sub-study Conclusions: AF

41 The adverse effects of forced ventricular desynchronization probably explain the difficulty in demonstrating a mortality and stroke benefit with physiologic (DDDR) compared to ventricular (VVIR) pacing in randomized trials. These investigators concluded that RV pacing imposes ventricular dyssynchrony even when AV synchrony is preserved, thereby increasing the risk of heart failure and AF. Sweeney MO, et al. Circulation 2003, in press MOST Sub-Study: Overall Conclusions

42 Dual-Chamber and VVI Implantable Defibrillator Trial DAVID

43 DAVID Trial Overview Hypothesis: Hypothesis: - - Aggressive management of LV dysfunction with optimized drug therapy and with dual chamber pacing could improve the combined endpoint of total mortality and hospitalization for heart failure, compared to similarly optimized drug therapy supported by ventricular backup pacing. Study design: Study design: - - Single blind, multicenter, parallel group, randomized trial comparing DDDR (70 bpm lower rate) vs. VVI (40 bpm lower rate) pacing modes Wilkoff B, et al. JAMA. 2002; 288:

44 DAVID Trial Protocol 760 assessed for eligibility 250 excluded 149 Did not meet Rx criteria 55 refused 46 Other 510 eligible 4 Not randomized 2 Required pacing 1 Inadequate defibrillation threshold 1 Decided not to implant 506 randomized VVI-40 (n=256)DDDR-70 (n= 250) 1 had pacing mode set to DDD 1 LTF 10 Discontinued intervention 5 Bradycardia 1 CHF and AF 1 Brady induced Torsade 1 Heart Tx workup 1 AF w rapid V response 1 multiple shocks due to double counting 3 had pacing mode set to VVI 2 LTF 5 Discontinued intervention 1 Angina 1 CHF and Lead Failure 1 CHF Hospitalization 1 Exacerbation of VT 1 Lead Migration Wilkoff B, et al. JAMA. 2002; 288:

45 DAVID Trial Results VVI-40DDDR-70HR (p-value, adj.) CHF Hospitalization or Death 16.1%26.7%1.61 (p = 0.03) CHF Hospitalization 13.3%22.6%1.54 (p=0.07) Death 6.5%10.1%1.61 (p=0.15) Wilkoff B, et al. JAMA. 2002; 288:

46 DAVID Wilkoff B, et al. JAMA. 2002; 288: VVI-40DDDR-70P-value 6-month EKG: Sinus97.1%42.0%<0.001 V-paced2.9%55.7%<0.001 QRSd ms ms <0.001 Cum % VP: 3 months 1.5% + 8.0% 57.9% % < months 0.6% + 1.7% 59.6% % < months 3.5% % 58.9% % <0.001

47 DAVID Conclusions Bradycardia pacing operation in dual- chamber ICDs should be optimized for individual patients. Bradycardia pacing operation in dual- chamber ICDs should be optimized for individual patients. -RV pacing in patients with LV dysfunction and no bradycardia indication for pacing can be harmful. -Programming of dual chamber devices to backup ventricular pacing is justified in this patient population. Wilkoff B, et al. JAMA. 2002; 288:

48 Left Ventricular-Based Cardiac Stimulation Post AV Nodal Ablation Evaluation (The PAVE Study) The PAVE study was a prospective, patient-blinded, randomized, multicenter clinical trial comparing chronic biventricular to right ventricular pacing in patients with chronic atrial fibrillation undergoing AV node ablation. The PAVE study was a prospective, patient-blinded, randomized, multicenter clinical trial comparing chronic biventricular to right ventricular pacing in patients with chronic atrial fibrillation undergoing AV node ablation.

49 PAVE Study ( J Cardiovasc Electrophysiol, Vol. 16, pp , November 2005)

50 PAVE Study Ablation of the AV node was permitted up to 4 weeks post-implantation Ablation of the AV node was permitted up to 4 weeks post-implantation Pacemaker was reprogrammed to a VVIR mode with a lower rate of 80 ppm for the next 4 weeks so to mitigate the risk of polymorphic ventricular tachycardia. All patients received rate-esponsive pacing, with the sensor optimized 4 weeks after implantation. Pacemaker was reprogrammed to a VVIR mode with a lower rate of 80 ppm for the next 4 weeks so to mitigate the risk of polymorphic ventricular tachycardia. All patients received rate-esponsive pacing, with the sensor optimized 4 weeks after implantation.

51 6-minute hallway walk distance (J Cardiovasc Electrophysiol, Vol. 16, pp , November 2005)

52 6-minute hallway walk distance For patients with symptomatic heart failure (NYHA Class II or III), the hallway walk distance measured at 6 months was 53% greater for patients randomized to biventricular pacing in comparison to patients receiving right ventricular pacing (78.9 ± 92.2 m vs 51.6 ± 86.2 m, P = 0.01). For patients with symptomatic heart failure (NYHA Class II or III), the hallway walk distance measured at 6 months was 53% greater for patients randomized to biventricular pacing in comparison to patients receiving right ventricular pacing (78.9 ± 92.2 m vs 51.6 ± 86.2 m, P = 0.01).

53 LV ejection Fraction (J Cardiovasc Electrophysiol, Vol. 16, pp , November 2005)

54 NYHA Class (J Cardiovasc Electrophysiol, Vol. 16, pp , November 2005)

55 (J Cardiovasc Electrophysiol, Vol. 16, pp , November 2005)

56 Mortality in PAVE Study There were 13 deaths (8%) in the biventricular pacing group and 19 deaths (18%) in the right ventricular pacing patients There were 13 deaths (8%) in the biventricular pacing group and 19 deaths (18%) in the right ventricular pacing patients

57 Conclusion of PAVE Study The findings of the PAVE study suggest that, in order to avoid the adverse effects of cardiac dyssynchrony generated by RV pacing, a biventricular pacing should be considered for patients who require AV node ablation for management of atrial fibrillation and who have a left ventricular ejection fraction ،ـ45% or who have NYHA Class II or III symptoms.

58 Multicenter Automatic Defibrillator Trial II (MADIT II) study During a 20-month follow-up, patients (n = 369) with ICD. During a 20-month follow-up, patients (n = 369) with ICD. ICD programming was not standardized, the development of new or worsened CHF was more common in the ICD arm (19.9%) compared with the conventionally treated patients (14.9%). ICD programming was not standardized, the development of new or worsened CHF was more common in the ICD arm (19.9%) compared with the conventionally treated patients (14.9%). The higher incidence of CHF in the ICD group was in all likelihood due to ventricular desynchronization rather than myocardial injury from ICD shocks The higher incidence of CHF in the ICD group was in all likelihood due to ventricular desynchronization rather than myocardial injury from ICD shocks

59 MADIT II Approximately 40% of the had dual chamber units (mostly set at DDD 60 to 70 beats/min) and 60% had single-chamber units (mostly set at VVI 60 beats/min). Approximately 40% of the had dual chamber units (mostly set at DDD 60 to 70 beats/min) and 60% had single-chamber units (mostly set at VVI 60 beats/min). Patients with dual-chamber units paced the ventricle about 85% of the time, whereas those with single-chamber units paced the ventricle only 15% of the time. Patients with dual-chamber units paced the ventricle about 85% of the time, whereas those with single-chamber units paced the ventricle only 15% of the time.

60 MADIT II During a 20-month follow-up, patients (n = 369) having high cumulative RV pacing (>50%), had a higher incidence of new or worsened heart failure and heart failure or death compared to patients with infrequent right ventricular pacing.

61 Conclusion of MADIT II study The slightly increased occurrence of heart failure was clearly associated with dual- chamber ICD units having a higher frequency of ventricular pacing. The slightly increased occurrence of heart failure was clearly associated with dual- chamber ICD units having a higher frequency of ventricular pacing.

62 Comparison of Medical Therapy, Pacing, and Defibrillation in Chronic Heart Failure (COMPANION) trial Cardiac resynchronization therapy with left ventricular pacing decreased the combined risk of death from any cause or first hospitalization in patients with advanced heart failure and prolonged QRS interval. Cardiac resynchronization therapy with left ventricular pacing decreased the combined risk of death from any cause or first hospitalization in patients with advanced heart failure and prolonged QRS interval.

63 COMPANION trial These investigators concluded that reduction in the combined endpoints of death and heart failure hospitalizations was primarily due to cardiac resynchronization therapy (CRT), since CRT and CRT with an ICD resulted in similar effects. These investigators concluded that reduction in the combined endpoints of death and heart failure hospitalizations was primarily due to cardiac resynchronization therapy (CRT), since CRT and CRT with an ICD resulted in similar effects.

64 What are the lessons learned from clinical trials? Conventional RV apical pacing results in “forced” ventricular desynchronization, which mimics LBBB and has adverse effects on ventricular structure and function.

65 Goals and Strategies to Optimize Ventricular Pacing

66 The New Goals of Pacing Therapy Several approaches have been investigated: Several approaches have been investigated: Manipulation of DDDR timing cycles (AV delay) to minimize unnecessary RV pacing Manipulation of DDDR timing cycles (AV delay) to minimize unnecessary RV pacing Use of AAI or DDI/R pacing modes Use of AAI or DDI/R pacing modes Novel pacing algorithms Novel pacing algorithms Alternate RV pacing sites Alternate RV pacing sites

67 Long AV Delays During Dual Chamber Pacing Long AV delays may reduce unnecessary ventricular pacing and maintain normal ventricular activation sequence but require reliable AV nodal conduction. Long AV delays may reduce unnecessary ventricular pacing and maintain normal ventricular activation sequence but require reliable AV nodal conduction.

68 Long AV Delays During Dual Chamber Pacing: An Incomplete Solution Long AV delays may impose limitations on optimal DDDR operation: Long AV delays may impose limitations on optimal DDDR operation: -Reduced 2:1 block point due to increased TARP -Abandonment of mode-switching or significantly delayed AF recognition -Susceptibility to endless loop tachycardias

69 Long AV delays do not sufficiently reduce ventricular pacing Two approaches to programming long AV delays to permit native ventricular activation: Two approaches to programming long AV delays to permit native ventricular activation: 1. AV delays > resting PR intervals1 AV delays > resting PR intervals (222  24 ms vs. 184  23 ms) Mean time Vp for all patients was 80%; > 50% for 88% 2. Long fixed AV delay (300 ms)2-3 Mean time Vp 17.7% overall but 39% in nearly 50% of patients Resting PQ interval (177  28 vs. 204  38), atrial stimulus-Q interval at 100 bpm (213  40 vs. 220  49) or AV delay (299  3.2 vs. 288  21) did not predict Vp High incidence of endless loop tachycardia Can be reduced if rate-adaptive AV delays are used 1 Sgarbossa E et al PACE 1993; ;16:872A. 2 Nielsen JC et al PACE 1997:20:1574A. 3 Nielsen JC et al Europace 1999;1:

70 AAI Pacing: Too Risky? AAI pacing preserves a normal ventricular activation sequence but requires stable long-term AV conduction and sinus rhythmAAI pacing preserves a normal ventricular activation sequence but requires stable long-term AV conduction and sinus rhythm SND is a spectrum of electrical disorders that includes AF and AV blockSND is a spectrum of electrical disorders that includes AF and AV block AAI pacing is ineffectual for ventricular bradycardia duringAAI pacing is ineffectual for ventricular bradycardia during – –Paroxysmal and permanent AF – –AV block

71 Development of Persistent (Complete) AV Block in Studies of Pacemaker Therapy for SND StudyMean Follow- Up Time Incidence of CHB Annualized Incidence Rosenqvist 1989 (literature review) 3 years Median 2.1% Range: % Median: 0.6% Range: 0-4.5% Andersen years 3.6%0.6% Brandt years 8.5%1.8% Sutton years 8.4%2.8% Rosenqvist years 4.0%2.0% Rosenqvist years 3.3%0.7% Hayes years 3.4%1.1%

72 Development of Chronic AF in Studies of Pacemaker Therapy for SND and CHB Study Pacing Mode Mean Follow-Up Time Incidence of AF Annualized Incidence Andersen 1997 AAI 5 years 8.8%1.8% Sutton 1986 AAI 3 years 4.5%1.5% Brandt 1992 AAI 5 years 7.0%1.4% PASE 1998 DDDR only 18 months 19.0%12.7% CTOPP 2000 DDDR/VVIR 3 years 16.6% 5.5% (DDDR)

73 DDIR Mode: A Limited Solution Permits long AV delays without the possibility of upper rate limit tracking during AF (unlike DDDR). Permits long AV delays without the possibility of upper rate limit tracking during AF (unlike DDDR). - However, limitations of long AV delays in reducing ventricular pacing still persist. Unique limitations imposed by DDIR mode Unique limitations imposed by DDIR mode - Operationally VVIR during AV block if sinus rate exceeds lower rate limit. -Competitive atrial pacing during sensor-modulation may precipitate AF. Can be mitigated with a non-competitive atrial pacing algorithm Can be mitigated with a non-competitive atrial pacing algorithm May be more applicable to the ICD population May be more applicable to the ICD population - Lower prevalence of AV block compared to conventional brady pacing population.

74 Novel Pacing Algorithms to Optimize Ventricular Pacing Current-generation devices have features that work to minimize ventricular pacing in appropriate patient populations: Current-generation devices have features that work to minimize ventricular pacing in appropriate patient populations: -Using Medtronic ’ s Search AV algorithm,27% and 47.2% reductions in ventricular pacing have been observed by Silverman and Ellenbogen, respectively, in patients with 1:1 conduction.1,2

75 Silverman et al, NASPE 2000 Novel Pacing Algorithms to Optimize Ventricular Pacing

76 Minimal ventricular pacing modes can be used in all patients, but are most effective in SND patients with reliable AV conduction and normal ventricular activation. Minimal ventricular pacing modes can be used in all patients, but are most effective in SND patients with reliable AV conduction and normal ventricular activation. Development will continue on new pacing algorithms which have been identified as an important means of minimizing ventricular pacing. Development will continue on new pacing algorithms which have been identified as an important means of minimizing ventricular pacing. Novel Pacing Algorithms to Optimize Ventricular Pacing

77 Alternate Sites of Ventricular Pacing Alternate site pacing : - Other right ventricular sites (outflow or septal sites) - Left ventricular sites in either unifocal or bifocal or biventricular modes.

78 Pace,Vol.29, March 2006 Alternate Site Pacing

79 Ongoing Studies of Alternate Site Pacing Pace,Vol.29, March 2006

80 Right Ventricular Outflow Tract (RVOT) Pacing A pooled analysis of nine prospective studies evaluating the hemodynamic effects of RVOT pacing in 217 patients indicated significant hemodynamic benefit compared with RV apical pacing.

81 Right Ventricular Outflow Tract (RVOT) Pacing Among these studies, most of them reported acute hemodynamic effects, while only two studies reported long-term hemodynamic effects, with one indicating no difference between the two sites after 3 months of pacing and the other reporting a significant increase in left ventricular fractional shortening following 2 months of right ventricular outflow tract.

82 RV Septal Pacing In an acute study of 14 patients receiving dual- chamber pacemaker for complete heart block, the septum was mapped to provide the narrowest QRS. The reduction of QRS duration obtained with right ventricular septal pacing correlated with homogenization of left ventricular contraction and improved systolic performance, albeit with minor differences in ejection fraction.

83 Shortest Distance to Purkinje Fibers? Right Ventricular Outflow Tract (RVOT) and/or Right Ventricular Septum

84 Prevention of Remodeling with Septal Pacing Karpawich (1991) Karpawich (1991) RV apical placement versus mid- septal placement Mid-septal lead position via appearance of normal paced QRS (no bundle branch block) Mid-septal lead position via appearance of normal paced QRS (no bundle branch block)Function Near normal ventricular conduction velocity Near normal ventricular conduction velocityHistology 4 month follow-up 4 month follow-up No calcification, degenerative changes, or altered mitochondrial morphology in the septal paced group No calcification, degenerative changes, or altered mitochondrial morphology in the septal paced group Karpawich PP, et al. Am Heart J 1991;121: RV Apical Pacing RV Septal Pacing LV Free Wall 4 months post Pacing

85 His Bundle Pacing His bundle pacing has been shown to result in the same QRS duration and pressure development as sinus rhythm and atrial pacing and better hemodynamics than RV apex pacing. Technical difficulties in applying such pacing relating to lead positioning, reliable capture, and long-term stability. Need for an intact bundle branch conduction system may be a limiting factor.

86 His Bundle Pacing A significant improvement in left ventricular performance was reported in 12 patients with a narrow QRS, chronic atrial fibrillation, and reduced ejection fraction (<40%). The same investigators were successful in applying this pacing technique in 39 of 54 patients with cardiomyopathy, low ejection fraction (mean 23%), persistent atrial fibrillation, and normal QRS (<120 ms). After a mean follow-up of 42 months, 29 patients were alive with improved symptoms and ejection fraction (mean 33%).

87 Bifocal RV Pacing (apical and outflow tract) Bifocal right ventricular (apical and outflow tract) pacing has been proposed for patients with heart failure where the coronary sinus approach to effect biventricular pacing turns out to be unsuccessful due to various reasons, such as failure to cannulate the os or to advance the lead.

88 Bifocal RV Pacing (apical and outflow tract) The long-term (over a 22-month period) clinical response of 22 patients undergoing this approach has been favorable with ensuing clinical improvement. In a subset of 50 patients with NYHA class II-III symptoms in the ROVA study, there was partial improvement reported with right ventricular bifocal pacing.

89 Bifocal RV Pacing (apical and outflow tract) More data about the usefulness of bifocal right ventricular pacing will be provided by the ongoing, randomized, single blind, crossover study (BRIGHT), which is recruiting patients with NYHA class III heart failure, a left ventricular ejection fraction <35%, LBBB, and QRS complex ≥120 ms.

90 Biventricular or Left Ventricular Pacing A few studies have compared RV apical pacing with LV or BiV pacing, which has now become the standard method to apply cardiac resynchronization therapy in patients with refractory heart failure. Overall, patients treated with BiV pacing had significantly greater improvement in QRS duration, 6-minute walk test, and quality-of life scores compared to RV pacing therapy.

91 Biventricular or Left Ventricular Pacing Preliminary data have indicated that there were no significant differences between single-site left ventricular pacing and biventricular pacing for cardiac resynchronization therapy suggesting that RV pacing may be redundant and left ventricular pacing alone might suffice.

92 Biventricular or Left Ventricular Pacing Acute hemodynamic measurements in 27 patients with heart failure having an epicardial left ventricular lead indicated that left ventricular pacing alone was superior to right ventricular pacing, but also to biventricular pacing as well. OPSITE, a prospective randomized trial, compared, in a single-blind, 3- month cross-over design, right ventricular and left ventricular pacing (phase 1) and right ventricular and biventricular pacing (phase 2). The study was performed in 56 patients affected by severely symptomatic permanent atrial fibrillation, uncontrolled ventricular rate, or heart failure. Primary endpoints were quality of life and exercise capacity, which were modestly improved mainly by biventricular, rather than left ventricular pacing.

93 Overall Conclusions First, for those patients already having conventional pacing systems, particularly in the presence of LV dysfunction or heart failure, pacemaker programming should be employed to minimize RV pacing. IN patients with sinus node dysfunction but with normal atrioventricular conduction, by establishing functional AAIR pacing with use of the DDDR mode with a long atrioventricular delay (≥250 ms). However, it remains an inefficient way to reduce ventricular pacing in at least 17–32%.

94 Overall Conclusions Manufacturers need to redesign their pacemakers to make such programming feasible or have the pacemakers search for atrioventricular conduction and withhold unnecessary ventricular pacing; automatic mode switching from AAIR to DDDR.

95 Overall Conclusions IN patients with permanent AV block, we need to use alternate sites of pacing for those receiving new pacing systems. For those patients who already have an implanted conventional pacemaker, either a dual-chamber pacing system in the presence of sinus rhythm or a single- chamber system in cases of permanent atrial fibrillation, we should seriously consider upgrading them to biventricular systems if moderate or severe left ventricular dysfunction is present.

96 The Donkey Analogy Ventricular dysfunction limits a patient's ability to perform the routine activities of daily living…

97 Digitalis Compounds Like the carrot placed in front of the donkey

98 Diuretics, ACE Inhibitors Reduce the number of sacks on the wagon

99 ß-Blockers Limit the donkey’s speed, thus saving energy

100 Cardiac Resynchronization Therapy Increase the donkey’s (heart) efficiency

101 Tehran Arrhythmia Clinic org


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