Modalities of Cardiac Stress Test Tiffany T. Nguyen MD April 2014

Objectives To understand the indications and contraindications for stress testing. To learn the different modalities of cardiac stress test. To effectively select the optimal cardiac stress test for each patient.

Indications Who to stress? Symptoms suggesting angina. Acute chest pain Recent ACS after 3 months of conservative therapy Known CHD and change in clinical status. Prior coronary revascularization. Valvular heart disease. New heart failure or cardiomyopathy. Chronic left ventricular dysfunction and CHD who are candidates for revascularization. Selected arrhythmias Undergoing non-urgent non-cardiac surgery.

Contraindications Who NOT to stress? Unstable angina Acute myocardial infarction Arrhythmia with hemodynamic instability Aortic dissection Symptomatic aortic stenosis Symptomatic severe heart failure Pulmonary embolism Myocarditis, Pericarditis Bottom line is do not stress while patient is symptomatic or if there is evidence of hemodynamic instability

Pre-Test Probability Age Nonanginal pain Atypical angina ACC/AHA 2012 Guidelines Low probability - <10% - no further testing, except for prognostic information. Intermediate probability - 10-90% - non-invasive testing for diagnosis (exercise ECG as first modality). High probability - >90% - non invasive testing for prognosis/management prior to cardiac cath. Age Nonanginal pain Atypical angina Typical angina Men Women 30-39 4% 2% 34% 12% 76% 26% 40-49 13% 3% 51% 22% 87% 55% 50-59 20% 7% 65% 31% 93% 73% 60-69 27% 14% 72% 94% 86% Please refer to CHEST PAIN mini lecture to determine if nonanginal vs atypical vs typical. It is important to keep in mind the pre-test probability of ACS when patient a presents with chest pain. Patient with low pre-test probability may not need cardiac stress test for diagnosis. However, there is prognostic implication for stress test. Stress test is indicated for all intermediate probability for diagnosis, with exercise ECG as first recommended modality. For patient with high pre-test probability, stress test is recommended not for diagnosis but for prognosis and guide invasive therapy (cath vs cabg).

Two Components Each cardiac imaging modality has two components: Stressing agent: treadmill, dobutamine, or adenosine Imaging agent: EKG, echo, or radionuclide tracer (thallium or technetium) Think of cardiac stress test as a combination of two components: How am I going to stress the heart? How can I collect information regarding the stressed heart?

Stressing Agents Stressor Pro Con Treadmill Physiologic, simple, less expensive, good for patient who can walk Dobutamine No exercise needed Caution in patients with arrhythmias Adenosine or dipyridamole (used with nuclear) No exercise needed; uncomfortable sensation of “heart stoppage” Adenosine may induce bronchospasm – caution in COPD and asthma! Slide courtesy of Dr. Varaz Bozoghlanian (Chief Resident 2012-2013) Dobutamine is a synthetic catecholamine that stimulates B1 receptor to increase HR and Contractility. Contraindication includes Arrhythmias (sustained Vtach) Recent MI or Unstable Angina Significant LV outflow obstruction Aortic dissection Moderate or Severe Hypertension (beware of this simple contraindication, very often test premature terminated due to hypertension). Adenosine works on A2A receptor causing coronary vasodilation. Areas with plaques do not vasodilate. This creates a difference in blood flow between well-perfused areas and diseased areas, which can be visualized with nuclear imaging. Regadenosone, binodenoson, apadenoson are selective A2A receptor and less risk of bronchospasm.

Imaging Agents Stressor Pro Con EKG Simple, less expensive Less information. May not be able to localize the lesion. Can not use if there are baseline EKG abnormalities i.e. LBBB with ST changes Echocardiogram Good if patient has pre-existing EKG abnormalities. More info than EKG. Less expensive than nuclear. Operator dependent to some extent. May have poor windows due to body habitus. Pre-existing wall motion abnormalities may make interpretation more challenging. Thallium or technetium Localizes ischemia and infarcted tissue. Expensive Slide courtesy of Dr. Varaz Bozoghlanian (Chief Resident 2012-2013)

Finally … What is a “MIBI?” What is a “Lexiscan?” Both are adenosine nuclear stress tests MIBI: the technetium molecule is attached to sestamibi molecule. The combined sestamibi-Technitium-99 molecule is aka “cardiolite” Lexiscan: uses a derivative of adenosine called regadenosine, which has 2-3 minute half-life instead of 30sec, so is easier to work with.

Sensitivity and Specificity Exercise EKG 68% 77% Stress Echo 76% 88% Nuclear Imaging 79-92% 73-88% Keep in mind of sensitivity and specificity of each modality.

Diagnosis or Prognosis Selecting Modalities Indication Diagnosis or Prognosis Localize Ischemia Exercise? Exercise? no no yes Pharmacologic test with Imaging yes Finally … Normal EKG Not on Digoxin No prior revascularization no Exercise Imaging yes Exercise EKG

Case Question A 60yo man is evaluated for chest pain of 4 months’ duration. He describes the pain as sharp, located in the left chest, with no radiation or associated symptoms, that occurred with walking one to two blocks and resolves with rest. Occasionally, the pain improves with continued walking or occurs during the evening hours. He has hypertension. Family history does not include cardiovascular disease in any first-degree relatives. His only medication is amlodipine. On physical examination, he is afebrile, blood pressure is 130/80mHg, pulse rate is 72/min, and respiration rate is 12/min. BMI is 28. No carotid bruits are present, and a normal S1 and S2 with no murmurs are heard. Lung fields are clear, and distal pulses are normal. EKG showed normal sinus rhythm.

Case Question Which of the following is the most appropriate diagnostic test to perform next? Adenosine nuclear perfusion stress test. Coronary angiography Echocardiography Exercise treadmill Answer D This patient has intermediate risk. His ability to exercise and normal ECG makes answer D the best modality.

Take Home Points Stress testing is indicated for patients with intermediate pre-test probability Each stress test has two components: an imaging modality and stress modality When determining which stress test to order, keep in mind their ability to exercise and whether any contraindications are present