Presentation on theme: "AF –pathophysiology and medical management"— Presentation transcript:
1AF –pathophysiology and medical management Dipin.SJunior residentmedicine
2Supraventricular tachy arrythmia charecterised by uncoordinated atrial activation and consequent deterioration of atrial mechanical function.
3ECG -rapid fibrillatory waves with changing morphology and rate and a ventricular rhythm that is irregularly irregularUsually originates near the pulmonary veins
4Classification of AF Diagnosis of AF New Onset AF Paroxysmal Up to 7 d Persistent > 7 daysPermanent CV failed
5Types of Atrial Fibrillation Paroxysmal AF: if it terminates spontaneously in fewer than 7 days (often in <24 h).Persistent AF: when it terminates either spontaneously after 7 days or following cardio version.Permanent AF: cardio version has failed or not attemptedRecurrent : after 2 or more episodes
6developed world- the most common causes are hypertension and coronary artery disease developing countries -hypertension, rheumatic valvular heart disease, and congenital heart disease are the most causesPresence of CHF markedly increases risk of AF
7factors Factors that trigger Factors that perpetuate Triggering foci of rapidly firing cells within the sleeve of atrial myocytes extending into the pulmonary veins - shown to be the underlying mechanism of most paroxysmal AF
8The pulmonary veins of patients with paroxysmal AF demonstrate abnormal properties of conduction Markedly reduced effective refractory period within the pulmonary veinsProgressive conduction delay within the pulmonary vein in response to rapid pacing or programmed stimulationConduction block between the pulmonary vein and the LAHeterogeneity of conduction promotes reentry within PV
9Other foci- the superior vena cava, the ligament of Marshall, the musculature of the coronary sinus, left atrial wall, crista terminalis of right atriaPrior to initiation-Primary increase in adrenergic tone followed by a marked vagal predominance (paroxysmal AF)Vagal stimulation shortens the refractory period of atrial myocardium with a nonuniform distribution .
10perpetuation The multiple wavelet hypothesis(More and colleagues) Fractionation of wavefronts traversing the atria into daughter wavelets.The number of wavelets at any moment depends on the refractory period, conduction velocity, and anatomic obstacles in different portions of the atria.
11Interstitial fibrosis predisposes to intraatrial reentry and AF(Li and colleagues) Delayed interatrial conduction and inhomogeneous dispersion of atrial refractory periodsLong-standing AF -loss of myofibrils, accumulation of glycogen granules, disruption in cell-to-cell coupling at gap junctions,and organelle aggregates
12AF itself produces alterations of atrial architecture that further contribute to atrial remodeling, mechanical dysfunction, and perpetuation of fibrillation.
13Myocardial stretch is an important mechanism of AF in the elderly. Altered stretch on atrial myocytes results in opening of stretch-activated channels.(L type Ca)AF produces electrical remodeling that promotes further AF.
14haemodynamics Loss of atrial contraction A rapid ventricular rate An irregular ventricular rhythmLoss of mechanical AV synchrony affects ventricular filling esp. when left ventricle has reduced compliance.
15The loss of AV synchrony results in a decrease in LVEDP (as the loading effect of atrial contraction is lost)Stroke volume and LV contractility are reduced (Frank starlings principle)Although there is a reduction in the LVEDP, there is an increase in the left atrial mean diastolic pressure
16Patients with restrictive physiology- pulmonary edema and hypotension may occur with AF In dilated cardiomyopathy – min. hemodynamic compromise if LV compliance is not affected .Patients with heart failure do worse when in AF1st clinical manifestation of AF may be CHF related to a tachycardia-induced cardiomyopathy.
17thromboembolism Thrombi mostly arise within the left atrial appendage Flow velocity in left atrial appendage is reduced during AFNitric oxide (NO) production in the left atrial endocardium is reducedIncrease in levels of the prothrombotic protein plasminogen activator inhibitor 1
18Objectives of Treatment Relief of Symptoms & Prevent recurrence-correction of rhythm disturbancePrevention of Systemic ThromboembolismTachycardia induced Myocardial Remodeling-rate control
19CHADS2 Scoring One Point Cardiac Failure Hypertension Age more than 75 DiabetesTwo PointsStroke or TIA, STE
20CHADS2 based Stroke Incidence CHADS2 Score (points)Adjusted Stroke Incidence % per year1.912.824.035.948.5512.5618.2Non valvular Atrial Fibrillation Rx with anticoagulation
21Risk Stratification Risk Factor Stratification Risk Factors to be AscertainedHigh Risk FactorsPrior Stroke/TIA or STE EventMitral stenosis , prosthetic valveModerate Risk FactorsAge >75, HF, HT, EF <35%, DMWeaker Risk FactorsFemale, CAD, Thyroid, yrs
22Antithrombotic Therapy for Patients With Atrial Fibrillation
2368% risk reduction with warfarin compared to placebo Target INR 2.5(2-3)Not only reduces frequency but severity and risk of death also.Relative risk reduction of 22% with aspirin compared to placeboNo difference in the indications for antithrombotic therapy between paroxysmal, persistent or permanent AF.
24Cardioversion antiarrhythmic drugs or the direct-current approach AF of <48 hours can be cardioverted without prior anticoagulationanticoagulation therapy is recommended for AF of uncertain duration.
252 strategiesOral warfarin with a therapeutic INR (2–3) for 3 to 4 weeks before cardioversion followed by continued warfarin thereafterTransesophageal echocardiography (TEE) and heparin immediately before cardioversion followed by oral warfarin thereafter.Left atria – stunning effect. So anticoagulation is to be continued for 4 wks
26Direct current cardioversion Anteriorly and posteriorly placed electrodesSynchronized to QRS complexInitial shock energy of 200J preferred ( higher energy less chance of VF)In AF> 3 mnths antiarrythmic drug started before cardioversion to prevent immediate or early reccurance
27AF lasting <1 wk – cardioversion -using oral flecainide, propafenone, dofetilide, and intravenous ibutilide.For longer duration- iv dofetilide( also amiodarone and ibutilide may be useful)Single oral dose of propafenone or flecainide – in recent onset AF (pill in the pocket)
28Rate control vs rhythm control The choice of strategy is determined by :paroxysmal or persistent AFseverity and type of symptomsassociated cardiac and other medical diseasesage of patientshort- and long-term treatment goalschoice of pharmacologic or nonpharmacologic therapyTry and maintain sinus rhythm in younger patients with AFIn the elderly, if symptoms can be controlled with a rate strategy, it is preferred.Anticoagulation is needed in patients at high risk for stroke regardless of whether a rate or rhythm strategy is chosen.
29Major Trials Comparing Rhythm Strategy and Rate Strategy Major trials include:AFFIRM (Atrial Fibrillation Follow-Up Investigation of Rhythm Management )RACE (rate control versus electrical cardioversion)PIAF (pharmacological intervention in AF)AF-CHFMajor overall findings:Rhythm-control strategy was not superior to rate-control strategy in terms of morbidity/mortalityAppropriate choice of therapy should be based on each patient’s symptoms and diseaserate control, prevention of thromboembolism, and correction of the rhythm disturbance - these strategies are not mutually exclusiveSeveral studies have compared rate control and rhythm control in patients with AFib. Major trials include AFFIRM, RACE, PIAF, STAF, HOT CAFÉ, and AF-CHF.1-6There were no differences in the primary end points in any of these studies. All the investigators concluded that rhythm control is not superior to rate control for the prevention of morbidity and mortality due to cardiovascular disease. However, it is important to keep in mind that appropriate therapy should be considered based on patient presentation, risk factors, and risk benefit ratio of the therapeutic option.1-6The next 2 slides examine each of these trials in greater detail.The AFFIRM Investigators. N Engl J Med. 2002;347: ;Van Gelder IC, et al. N Engl J Med. 2002;347: ; 3. Hohnloser SH, et al. Lancet. 2000;356: ;4. Carlsson J, et al. J Am Coll Cardiol. 2003;41: ; 5. Opolski G, et al. Chest. 2004;126: ; 6. Roy D, et al. N Engl J Med. 2008;358: ;7. Fuster V, et al. Circulation. 2006;114:e257-e354.1. The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Investigators. A comparison of rate control and rhythm control in patients with atrial fibrillation. N Engl J Med. 2002;347:2. Van Gelder IC, Hagens VE, Bosker HA, et al. A comparison of rate control and rhythm control in patients with recurrent persistent atrial fibrillation. N Engl J Med. 2002;347:3. Carlsson J, Miketic S, Windeler J, et al. Randomized trial of rate-control versus rhythm-control in persistent atrial fibrillation: the Strategies of Treatment of Atrial Fibrillation (STAF) study. J Am Coll Cardiol. 2003;41:4. Hohnloser SH, Kuck KH, Lilienthal J. Rhythm or rate control in atrial fibrillation - Pharmacological Intervention in Atrial Fibrillation (PIAF): a randomised trial. Lancet. 2000;356:5. Opolski G, Torbicki A, Kosior DA, et al. Rate control vs rhythm control in patients with nonvalvular persistent atrial fibrillation: the results of the Polish How to Treat Chronic Atrial Fibrillation (HOT CAFE) Study. Chest. 2004;126(2):6. Roy D, Talajic M, Nattel S, et al. Rhythm control versus rate control for atrial fibrillation and heart failure. N Engl J Med ;358:
30Control of ventricular rate In the acute phase, iv diltiazem, metoprolol, esmolol, or verapamil (slowing of AV nodal conduction within 5 minutes)Iv digoxin is less usefulIn chronic phase- digoxin gives good control of resting heart rateBeta blockers and CCBs during exercise.Chronically elevated vent. Rates despite drug therapy- AV nodal ablation
31Maintenance of sinus rythm Avoidance of inciting factorSafety first principle in selecting antiarrythmicsClass Ic drugs are to combined with AV nodal blockersMonitor QRS duration with class Ic(150% increase-reduce drug)Monitor QT interval with sotalol and amiodarone
32Antiarrhythmic drug therapy to maintain sinus rhythm in patients with recurrent paroxysmal or persistent atrial fibrillation