Exercise stress ecg. dmo


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Exercise stress ecg. dmo

  1. 1. Exercise stress testing Dr Shivanand Patil
  2. 2. General Applications <ul><li>Diagnosis : Who has coronary artery disease </li></ul><ul><li>Prognosis : Who is high risk? Who needs intervention </li></ul><ul><li>Functional assessment : Who is disabled? What activities can be done safely? </li></ul><ul><li>Treatment assessment : Is medication or intervention effective? </li></ul>
  3. 3. METABOLIC EQUIVALENT <ul><li>Unit of sitting , resting O2 uptake </li></ul><ul><li>1 MET = 3.5 ml O 2 / kg / min </li></ul><ul><li>Measured VO2 =NO.Of METS 3.5ml O2/Kg/min </li></ul><ul><li>Asses disability </li></ul><ul><li>Standardize different protocols </li></ul>
  5. 6. Mason –Likar modification <ul><li>Extremity electrodes moved to the torso to reduce motion artifact </li></ul><ul><li>Arm electrodes - lateral aspects of infraclavicular fossae </li></ul><ul><li>Leg electrodes -above the anterior iliac crest and below the rib cage </li></ul>
  6. 7. Mason –Likar modification <ul><li>It results in </li></ul><ul><li>Right axis shift </li></ul><ul><li>Increased voltage in inferior leads </li></ul><ul><li>May produce loss of inferior Q waves and development of new Q waves in lead aVL </li></ul><ul><li>Thus, the body torso limb lead positions cannot be used to interpret a diagnostic rest 12-lead ECG </li></ul>
  7. 8. Mason –Likar modification
  8. 9. Baseline Abnormalities - Obscure ECG changes during exercise <ul><li>Left bundle branch block </li></ul><ul><li>LVH with repolarization abnormality </li></ul><ul><li>Digitalis Therapy </li></ul><ul><li>Ventricular paced rhythm </li></ul><ul><li>WPW syndrome </li></ul><ul><li>ST abnormality associated with SVT (or) AF </li></ul><ul><li>ST abnormalities with MVPS and severe anemia </li></ul>
  9. 10. Types of ST Segment Displacement <ul><li>In normal persons </li></ul><ul><li>The PR, QRS, and QT intervals shorten as heart rate increases </li></ul><ul><li>P amplitude increases </li></ul><ul><li>PR segment becomes progressively more downsloping in the inferior leads </li></ul><ul><li>J point or junctional depression will occur </li></ul>
  10. 11. Normal
  11. 12. Types of ST Segment Displacement <ul><li>In patients with myocardial ischemia </li></ul><ul><li>ST segment usually becomes more horizontal (flattens) as the severity of the ischemic response worsens. </li></ul><ul><li>With progressive exercise, the depth of ST segment depression may increase, involving more ECG leads, and the patient may develop angina </li></ul>
  12. 13. Abnormal
  13. 14. False-positive
  14. 15. Types of ST Segment Displacement <ul><li>In the immediate postrecovery phase </li></ul><ul><li>ST segment displacement may persist, with downsloping ST segments and T wave inversion, gradually returning to baseline after 5 to 10 minutes </li></ul><ul><li>Ischemic response ---only in the recovery phase </li></ul><ul><li>Occur in 10 percent of patients </li></ul><ul><li>Prevalence is higher in asymptomatic populations compared with those with symptomatic CAD </li></ul>
  15. 16. Different ECG patterns
  16. 17. MEASUREMENT OF ST SEGMENT DISPLACEMENT <ul><li>True isoelectric point ----TP segment </li></ul><ul><li>For purposes of interpretation--- PQ junction is usually chosen as the isoelectric point </li></ul><ul><li>Abnormal response </li></ul><ul><li>The development of 1 mm or greater of J point depression </li></ul><ul><li>with a relatively flat ST segment slope (<1 mV/sec ) </li></ul><ul><li>depressed greater than or equal to 0.10 mV 80 msec after the J point (ST 80) in three consecutive beats with a stable baseline </li></ul>
  17. 18. Ischemic exercise-induced ECG
  18. 19. MEASUREMENT OF ST SEGMENT DISPLACEMENT <ul><li>When the ST 80 measurement is difficult to determine at rapid heart rates (e.g., >130 beats/min), the ST 60 measurement should be used. </li></ul><ul><li>The ST segment at rest may occasionally be depressed. When this occurs, the J point and ST 60 or ST 80 measurements should be depressed an additional 0.10 mV or greater to be considered </li></ul><ul><li>When the degree of resting ST segment depression is 0.1 mV or greater, the exercise ECG becomes less specific, and myocardial imaging modalities should be considered </li></ul>
  19. 20. MEASUREMENT OF ST SEGMENT DISPLACEMENT <ul><li>In early repolarization </li></ul><ul><li>Normal response---Resting ST segment elevation returns to the PQ junction </li></ul><ul><li>Magnitude of exercise-induced ST segment depression should be determined from the PQ junction and not from the elevated position of the J point before exercise </li></ul>
  20. 21. MEASUREMENT OF ST SEGMENT DISPLACEMENT <ul><li>Localization of site of myocardial ischemia </li></ul><ul><li>ST segment depression do not localize the site of myocardial ischemia and which coronary artery is involved </li></ul><ul><li>ST segment elevation is relatively specific for the territory of myocardial ischemia and the coronary artery involved. </li></ul>
  21. 22. UPSLOPING ST SEGMENTS <ul><li>Normal response </li></ul><ul><li>J point depression </li></ul><ul><li>Rapid upsloping ST segment (>1 mV/sec) </li></ul><ul><li>depressed less than 1.5 mm after the J-point </li></ul><ul><li>Abnormal response </li></ul><ul><li>Depression of ST segment > 1.5 mm at ST80 </li></ul><ul><li>Patients with a high CAD prevalence--- abnormal. </li></ul><ul><li>Asymptomatic or with a low CAD prevalence--- less certain. </li></ul>
  22. 23. ST SEGMENT ELEVATION <ul><li>ST segment elevation may occur in </li></ul><ul><li>an infarct territory where Q waves are present </li></ul><ul><li>in a noninfarct territory. </li></ul><ul><li>Abnormal response </li></ul><ul><li>1 mm elevation at ST60 for 3 consecutive beats with a stable baseline. </li></ul>
  23. 24. ST SEGMENT ELEVATION <ul><li>ST segment elevation in leads with abnormal Q waves </li></ul><ul><li>Occur in 30% of anterior MI & 15% of inferior MI </li></ul><ul><li>Have a lower ejection fraction </li></ul><ul><li>greater severity of resting wall motion abnormalities </li></ul><ul><li>worse prognosis. </li></ul><ul><li>not a marker of more extensive CAD </li></ul><ul><li>rarely indicates myocardial ischemia. </li></ul>
  24. 25. ST SEGMENT ELEVATION <ul><li>ST segment elevation in leads without Q waves </li></ul><ul><li>Indicates transmural myocardial ischemia caused by coronary vasospasm or a high-grade coronary narrowing </li></ul><ul><li>Occurring in a 1 percent of patients with obstructive CAD. </li></ul><ul><li>Site of ST segment elevation is relatively specific for the coronary artery involved </li></ul>
  26. 27. T WAVE CHANGES <ul><li>Pseudonormalization of T waves </li></ul><ul><li>T-waves inverted at rest and becoming upright with exercise </li></ul><ul><li>Nondiagnostic finding --- in low CAD prevalence populations </li></ul><ul><li>In rare instance--- marker for myocardial ischemia </li></ul>
  27. 28. Pseudonormalization of T waves
  28. 29. OTHER ECG MARKERS <ul><li>Changes in R wave amplitude </li></ul><ul><li>Relatively nonspecific and are related to the level of exercise performed </li></ul><ul><li>In LVH the ST segment response cannot be used reliably to diagnose CAD </li></ul><ul><li>U wave inversion </li></ul><ul><li>may occasionally be seen in the precordial leads at heart rates of 120 beats/min </li></ul><ul><li>Relatively specific and relatively insensitive for CAD </li></ul>
  30. 31. Blood Pressure <ul><li>Normal Exercise response </li></ul><ul><li>SBP - Increase to 160 to 200 mm HG </li></ul><ul><li>DBP - Does not change significantly </li></ul><ul><li>In LV dysfunction (or) an excessive reduction in systemic vascular resistance </li></ul><ul><li>Failure to increase SBP> 120 mm HG </li></ul><ul><li>(or) Sustained decrease > 10 mm HG </li></ul><ul><li>(or) Fall in SBP below standing rest values </li></ul>
  31. 32. Exertional Hypotension <ul><li>Ranges from 3 to 9 % </li></ul><ul><li>Higher in patients with TVD (or) Left main CAD </li></ul><ul><li>Cardiomyopathy </li></ul><ul><li>Cardiac arrhythmias </li></ul><ul><li>Vasovagal reactions </li></ul><ul><li>LVOT Obstruction </li></ul><ul><li>On Antihypertensive drugs </li></ul><ul><li>Hypovolemia </li></ul><ul><li>Prolonged Vigorous Exercise </li></ul>
  32. 33. Work Capacity <ul><li>Limited work capacity </li></ul><ul><ul><li>Associated with increased risk of cardiac events in known(or) suspected CAD </li></ul></ul><ul><li>In estimating functional capacity, the amount of work performed (or exercise stage achieved ) should be the parameter measured and not the number of minutes of exercise </li></ul>
  33. 34. Sub-Maximal Exercise <ul><li>APMHR (Age Predicted Maximum Heart Rate) = 220 - Age </li></ul><ul><li>Patient should achieve atleast 85 - 90 % of APMHR to test the cardiac reserve </li></ul><ul><li>Non - Diagnostic Test </li></ul><ul><ul><li>PVD </li></ul></ul><ul><ul><li>Orthopedic Limitation </li></ul></ul><ul><ul><li>Neurological Impairment </li></ul></ul><ul><ul><li>Poor Motivation </li></ul></ul>
  34. 35. Heart Rate Response <ul><li>Inappropriate increase in heart rate at low exercise workloads </li></ul><ul><ul><li>Atrial fibrillation </li></ul></ul><ul><ul><li>Physically Deconditioned </li></ul></ul><ul><ul><li>hypovolemic </li></ul></ul><ul><ul><li>Anaemic </li></ul></ul><ul><ul><li>Marginal LV function </li></ul></ul>
  35. 36. Heart Rate Response <ul><li>Chronotropic incompetence </li></ul><ul><ul><li>Heart rate increment per stage of exercise that is less than normal (or) a peak rate below predicted at maximal work loads </li></ul></ul><ul><li>Occurs in </li></ul><ul><ul><li>sinus node disease </li></ul></ul><ul><ul><li>Beta Blocker </li></ul></ul><ul><ul><li>Compensated CCF </li></ul></ul><ul><ul><li>Myocardial ischemic response </li></ul></ul>
  36. 37. Rate-Pressure Product <ul><li>Heart rate x Systolic BP Product </li></ul><ul><li>Indirect measure of myocardial oxygen demand </li></ul><ul><li>increases progressively with exercise </li></ul><ul><li>used to characterize cardiovascular performance </li></ul><ul><li>Normal - 20 to 35 mm HG x beats/m x 10 -3 </li></ul><ul><li>In CAD - < 25 mm HG x beats/m x 10 -3 </li></ul>
  37. 38. Chest discomfort <ul><li>It occurs usually after the onset of ischemic ST segment depression </li></ul><ul><li>In some patients , it may be the only signal of obstructive CAD </li></ul><ul><li>In CSA , Chest discomfort occurs less frequently than ischemic ST segment depression </li></ul>
  38. 39. Diagnostic use of Exercise testing
  39. 40. Sensitivity and Specificity <ul><li>Both varies with the population being tested </li></ul><ul><li>Exercise ECG is best used in </li></ul><ul><li>The evaluation of a patient at intermediate risk with an atypical history (pre-test probability-30-70%) </li></ul><ul><li>Patient at low risk with a typical history </li></ul>
  40. 41. Sensitivity and Specificity 66% 53% 81% 86% Multivessel CAD Left main or TVD --- 25-71% LAD>RCA>LCx SVD 77% 68% In CAD (General) Specificity Sensitivity Patients
  41. 42. Limitations <ul><li>Bayes theorem </li></ul><ul><li>The probability of a positive test result is affected by the likelihood (conditional probability) of positive test result among the population that has undergone the test (pretest probability) </li></ul><ul><li>The higher the probability that a disease is present in a given individual before a test is ordered, the higher is the probability that a test result is true-positive </li></ul>
  42. 43. Noncoronary causes of ST segment depression <ul><li>Severe aortic stenosis </li></ul><ul><li>Severe hypertension </li></ul><ul><li>Cardiomyopathy </li></ul><ul><li>Anemia </li></ul><ul><li>Hypokalemia </li></ul><ul><li>Severe hypoxia </li></ul><ul><li>Digitalis use </li></ul><ul><li>Sudden excessive exercise </li></ul>
  43. 44. Noncoronary causes of ST segment depression <ul><li>Glucose load </li></ul><ul><li>Left ventricular hypertrophy </li></ul><ul><li>Hyperventilation </li></ul><ul><li>Mitral valve prolapse </li></ul><ul><li>Interventricular conduction disturbance </li></ul><ul><li>Preexitation syndrome </li></ul><ul><li>Severe volume overload (aortic,mitral regurgitation) </li></ul><ul><li>Supraventricular tacyarrhythmias </li></ul>
  44. 45. Adverse prognosis and multivessel CAD <ul><li>Duration of symptom-limiting < 6 METS </li></ul><ul><li>Failure to increase SBP >120 mm hg , or a sustained decrease >10 mm hg , or below rest levels, during progressive exercise </li></ul><ul><li>ST segment depression > 2mm , downsloping ST segment, starting at < 6 METS , involving > 5 leads, persisting > 5 min into recovery </li></ul>
  45. 46. Adverse prognosis and multivessel CAD <ul><li>Exercise–induced ST segment elevation (avr excluded) </li></ul><ul><li>Angina pectoris at low exercise workloads </li></ul><ul><li>Reproducible sustained (>30 sec) or symptomatic ventricular tacycardia </li></ul>
  46. 47. Exercise testing in determining prognosis
  47. 48. Symptomatic Patients <ul><li>TMT should be performed, before coronary Angiography -in patients with chronic CAD </li></ul><ul><li>Excellent exercise tolerance ( > 10 Mets) usually have an excellent prognosis regardless of the anatomical extent of CAD </li></ul>
  48. 49. After Myocardial infarction <ul><li>TMT is useful to determine </li></ul><ul><ul><li>Risk stratification and assessment of prognosis </li></ul></ul><ul><ul><li>functional capacity activity prescription after hospital discharge </li></ul></ul><ul><ul><li>Assessment of adequacy of medical therapy </li></ul></ul>
  49. 50. Cardiac Arrhythmias and conduction disturbances
  50. 51. Ventricular Premature Contraction <ul><li>Occurs frequently during exercise testing and increase with age </li></ul><ul><li>not a useful marker of CAD in the absence of ischemic ST segment depression </li></ul>
  51. 54. <ul><ul><li>In LBBB - Exercised induced ST segment depression is found in most patients - cannot be used as diagnostic of prognostic indicator </li></ul></ul><ul><ul><li>In RBBB - Exercise induced ST depression in leads V1 - V4 is common finding and is non diagnostic of CAD </li></ul></ul>
  52. 55. Supraventricular Arrhythmias <ul><li>Presence of SVT is not diagnostic for CAD </li></ul>
  53. 56. Pre-Excitation Syndrome <ul><li>Disappearance of delta waves occurs while exercise in 20 - 50 % of cases </li></ul><ul><ul><li>Abrupt disappearance – Good prognosis </li></ul></ul><ul><li>Presence of WPW syndrome, invalidates the use of ST segment analysis as a diagnostic method for detecting CAD </li></ul>
  54. 57. Special Clinical Applications <ul><li>Digitalis - Produce exertional ST depression </li></ul><ul><li>Hypokalemia - associated with ST depression </li></ul><ul><li>Antischemic therapy </li></ul><ul><ul><li>prolongs the time of onset of ST depression </li></ul></ul><ul><ul><li>Increase exercise tolerance </li></ul></ul><ul><ul><li>normalize exercise ECG response.(10 to 15 %) </li></ul></ul><ul><li>Heparin therapy </li></ul><ul><ul><li>increase total exercise duration </li></ul></ul>
  55. 58. Special Clinical Applications <ul><li>In women </li></ul><ul><ul><li>Sensitivity and specificity are less in women than men </li></ul></ul><ul><ul><li>False positive tests - due to greater release of catacholamines during exercise produce vasoconstriction </li></ul></ul><ul><ul><ul><li>more common during menses (or) preovulation </li></ul></ul></ul>
  56. 59. Special Clinical Applications <ul><li>Hypertension </li></ul><ul><ul><li>In normotensive asymptomatic individuals- increased long term risk is found in </li></ul></ul><ul><ul><ul><li>increased SBP > 214 mm HG </li></ul></ul></ul><ul><ul><ul><li>increased SBP (or) DBP at 3rd minute of recovery </li></ul></ul></ul><ul><ul><li>Severe systemic hypertension cause exercise induced ST depression in the absence of atherosclerosis </li></ul></ul><ul><ul><li>Exercise tolerance is decreased in patients with poor blood pressure control </li></ul></ul>
  57. 60. Special Clinical Applications <ul><li>In elderly patients </li></ul><ul><ul><li>cardiac arrhythmias , chronotropic incompetence and hypertension responses are more common </li></ul></ul><ul><li>Diabetes Mellitus </li></ul><ul><ul><li>in patients with autonomic dysfunction and sensory neuropathy , anginal threshold may be increased </li></ul></ul>
  58. 61. Special Clinical Applications <ul><li>After CABG </li></ul><ul><ul><li>indicate graft occlusion , stenosis or progression of CAD </li></ul></ul><ul><li>After PTCA </li></ul><ul><ul><li>In asymptomatic patients , 6 months post procedural test allows to diagnose restenosis </li></ul></ul>
  59. 62. Indications for terminating exercise testing
  60. 63. Indications for terminating exercise testing
  61. 64. CONTRAINDICATIONS <ul><li>ABSOLUTE </li></ul><ul><li>RELATIVE </li></ul>
  62. 65. CONTRAINDICATIONS TO EXERCISE TESTING (ACC/AHA) <ul><li>ABSOLUTE </li></ul><ul><li>Acute MI (within 2 d) </li></ul><ul><li>USAP high risk </li></ul><ul><li>Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise </li></ul><ul><li>Symptomatic severe AS </li></ul>
  63. 66. CONTRAINDICATIONS TO EXERCISE TESTING (ACC/AHA )… <ul><li>ABSOLUTE … </li></ul><ul><li>Uncontrolled symptomatic HF </li></ul><ul><li>Acute pulmonary embolus or pulmonary infarction </li></ul><ul><li>Acute myocarditis or pericarditis </li></ul><ul><li>Acute aortic dissection </li></ul>
  64. 67. CONTRAINDICATIONS TO EXERCISE TESTING (ACC/AHA ) <ul><li>RELATIVE </li></ul><ul><li>Left main coronary stenosis </li></ul><ul><li>Moderate stenotic valvular heart disease </li></ul><ul><li>Electrolyte abnormalities </li></ul><ul><li>Severe arterial hypertension  200/110 </li></ul>
  65. 68. CONTRAINDICATIONS TO EXERCISE TESTING (ACC/AHA )… <ul><li>RELATIVE … </li></ul><ul><li>Tachyarrhythmias or bradyarrhythmias </li></ul><ul><li>Hypertrophic cardiomyopathy and other forms of outflow tract obstruction </li></ul><ul><li>Mental or physical impairment leading to an inability to exercise adequately </li></ul><ul><li>High-degree AV block </li></ul>
  66. 69. TMT Report <ul><li>Exercise protocol used </li></ul><ul><li>Duration of exercise </li></ul><ul><li>Peak treadmill speed and grade </li></ul><ul><li>Peak workload in MET or VO2 max </li></ul><ul><li>Functional Capacity </li></ul><ul><li>Maximum heart rate percentage of APMHR </li></ul><ul><li>Resting and Peak Blood Pressure </li></ul><ul><li>Symptoms </li></ul><ul><li>Arrhythmias </li></ul><ul><li>ECG Changes </li></ul>
  67. 70. Thank You
  68. 71. Work Capacity in METS-Women
  69. 72. Work Capacity in METS-Men
  70. 73. Terms-Evalution of test results <ul><li>True positive(TP) = abnormal test results in individual with disease </li></ul><ul><li>False positive(FP) = abnormal test results in individual without disease </li></ul><ul><li>True negative(TN) = normal test result in individual without disease </li></ul><ul><li>Likelihood ratio: odds of a test result being true </li></ul><ul><li>of an abnormal test: sensitivity/(1-specifity) </li></ul><ul><li>Of a normal test: specificity/(1-Sensitivity) </li></ul>
  71. 74. Terms-Evalution of test results <ul><li>Sensitivity: % of patients with CAD who have an abnormal result= TP/(TP+FN) </li></ul><ul><li>Specificity: % of patients without CAD who have a normal results =TN/(TN+FP) </li></ul><ul><li>Predictive value: % of patients with abnormal result who have CAD= TN/(TN+FN) </li></ul><ul><li>Test accuracy: % of true test=(TP+TN)/total no. of tests performed </li></ul><ul><li>Relative risk: Disease rate in persons with a positive test result/ Negative test result </li></ul>
  72. 75. Pretest probability of CAD Low Very low Intermediate Very low Intermediate Low High Intermediate 40-49 Men Women Very low Very low Low Very low Intermediate Very low Intermediate Intermediate 30-39 Men Women Asymptomatic Nonanginal Chest pain Atypical or Probable angina Typical or Definite angina Age/ Sex
  73. 76. Pretest probability of CAD Low Low Intermediate Intermediate Intermediate Intermediate High High 60-69 Men Women Low Very low Intermediate Low Intermediate Intermediate High Intermediate 50-59 Men Women Asymptomatic Nonanginal Chest pain Atypical or Probable angina Typical or Definite angina Age/ Sex
  74. 77. Duke treadmill score
  75. 78. Duke Treadmill Score <ul><li>Exercise time - ( 5 x ST deviation ) - (4 x Treadmill angina index) </li></ul><ul><li>used to identify prognostic , intermediate - high risk patients in whom coronary angiography would be indicated to define coronary anatomy </li></ul><ul><li>Low-risk patients - scores of five or higher </li></ul><ul><li>Intermediate risk -scores between five and –10 </li></ul><ul><li>High risk -scores lower than -10 </li></ul>
  76. 79. PROGNOSTIC SCORES <ul><li>DUKE treadmill score - by mark etal in Exercise time - (5 x max. ST depression) - 4 x 1987, based on 2842 patients. </li></ul><ul><li>angina index. </li></ul><ul><li>5 YEARS SURVIVAL : </li></ul><ul><li>> 5 - 97% </li></ul><ul><li>- 10 to 4 - 91% </li></ul><ul><li>< - 10 - 72% </li></ul><ul><li>Score contains prognostic information even after clinical and cath data. </li></ul><ul><li>Prognostic stratifing power greatest in 3 VD and lowest in SVD. </li></ul>
  77. 80. VETERENS AFFAIRS (VA) SCORE <ul><ul><ul><ul><ul><li>H/O CHF / digoxin </li></ul></ul></ul></ul></ul><ul><li>Change in systolic BP. </li></ul><ul><li>METS achieved. </li></ul><ul><li>VA score = 5 x (CHF / digoxin) + ST depression + change in SBP - METS. </li></ul><ul><li>< -2 low risk (annual mortality 1%) </li></ul><ul><li>-2 to 2 moderate risk (annual mortality 7%) </li></ul><ul><li>> 2 high risk (annual mortality 15%) </li></ul>
  79. 82. Special applications <ul><li>After myocardial infarction/ unstable angina </li></ul><ul><li>Cardiac rehabilitation </li></ul><ul><li>Screening </li></ul><ul><li>Exercise prescription </li></ul><ul><li>Preoperation evaluation </li></ul><ul><li>Dysrhythmias </li></ul><ul><li>Intermittent claudication/Pulmonary disease </li></ul>
  80. 83. Asymptomatic Population <ul><li>Abnormal ECG </li></ul><ul><ul><li>Prevalance in Men - 5 to 12 % </li></ul></ul><ul><ul><li>Prevalance in Women - 20 to 30 % </li></ul></ul><ul><ul><li>Risk of development of cardiac events - 9 times more than normal </li></ul></ul><ul><ul><li>Cardiac events over 5 years - 25 % </li></ul></ul><ul><ul><li>Most common Cardiac event - Angina </li></ul></ul><ul><ul><li>Prognostic value of an ST segment shift in women is less than in men </li></ul></ul>
  81. 84. Ventricular Premature Contraction <ul><li>In CAD occurs in 20 % of patients </li></ul><ul><li>In SCD survivors - 50 to 75 % </li></ul><ul><li>More frequent during recovery phase </li></ul><ul><li>Suppressed by B - Blocker therapy </li></ul><ul><li>Exercise testing provokes repetitive VPC’s in patients with H/O sustained VT </li></ul>