SUMMARY The sensitivity of myocardial perfusion imaging (MPI) using thallium-201 injected both at rest and during peak exercise was compared to simultaneously recorded 12 lead electrocardiography (ECG) for the detection of transient ischemia in 20 normal subjects and 63 patients with coronary artery disease (CAD). No significant perfusion defects or ECG changes were seen on either the rest or exercise studies in any of the normal subjects. Fifty-six percent of patients with CAD developed new perfusion defects with exercise compared to 38% who developed ischemic ST-segment depression (P < 0.02). However, when chest pain and/or ST depression were considered indices of ischemia, the sensitivity of exercise testing and thallium-201 MPI was similar. The increased sensitivity of MPI compared to ST-segment depression on the ECG was due to patients MYOCARDIAL PERFUSION IMAGING (MPI) with radioactive tracers offers a noninvasive method for detecting myocardial infarction and transient myocardial ischemia. The clinical use of cationic tracers such as potassium-43 and rubidium-811-4 is based upon the principle that tracer uptake by myocardial cells is proportional to regional myocardial blood flow. Myocardial areas supplied by critically narrowed coronary arteries may demonstrate normal tracer uptake at rest, but when tracer is injected during exercise they may show relatively decreased concentration in comparison to normally perfused areas. A region of absent tracer uptake with injection at rest, not changing when tracer is injected during exercise, suggests the presence of myocardial infarction or scarring, while a new perfusion defect appearing with injection during exercise, suggests an area of transient myocardial ischemia.Although experience with exercise injected myocardial perfusion imaging is limited there is evidence to suggest that the technique may be more sensitive than exercise electrocardiography (ECG) in identifying patients with coronary artery disease.' Thallium-201 (TI 201) has biologic properties similar to potassium-43 and rubidium-81. The physical properties of T1 201 are, however, better suited to obtaining high resolu- with baseline ECG abnormalities and those who failed to achieve 85% of predicted maximum heart rate with exercise. Analysis of the exercise results according to the extent of coronary artery disease revealed a progressive increase in both positive ECGs and MPI with the number of vessels involved. In patients with single vessel disease the MPI was more sensitive than the ECG (P < 0.02).The combination of the rest and exercise ECG, MPI and chest pain during exercise failed to identify 11% of patients with CAD.Exercise thallium-201 MPI is a useful adjunct to conventional exercise testing particularly when evaluating patients with abnormal resting ECGs, those who develop ventricular conduction defects or arrhythmias during exercise, and those who fail to achieve their predicted heart rate because of fatigue or breathlessness.tion images with currently available nuclear imaging equipment....

Patients who survive an acute myocardiac infarction (AMI) have significant coronary disease and are at risk for angina pectoris, recurrent myocardiac infarction and sudden death. This study provides data gathered prospectively for 106 patients surviving myocardial infarction who had coronary arteriography, left ventriculography and 24-hour electrocadiographic recordings before hospital discharge and were followed 30 months. Univariate analysis showed that low ejection fraction, proximal left anterior descending coronary disease and significant disease in all three coronary arteries were associated with a high risk of sudden cardial death. The ECG location or type of infarction was not helpful in predicting mortality, reinfarction or continuing angina. Multivariate analysis of 30 clinical and laboratory variables identified previous myocardial infarction and an ejection fraction less than 40% as the best predictors of mortality; all 13 patients who died were identified by these two variables. Three-vessel coronary artery disease, proximal left coronary disease and complicated late hospital-phase ventricular arrhythmias did not provide additional information about mortality once the information provided by the first two variables was considered. Multivariate analysis identified hypertension, three-vessel coronary disease, postinfarction angina pectoris and previous AMI as significant predictors of recurrent AMI during the 30 month follow-up.

Background. Two hundred eighteen patients were evaluated in a two-phase approach (time to first appropriate discharge, survival after discharge) to identify factors that may be related to maximal benefit derived from use of an automatic implantable cardioverter-defibrillator (AICD).Methods and Results. One hundred ninety-seven patients survived implantation of AICD, with or without concomitant cardiac surgery. One hundred five patients had an AICD discharge associated with syncope, presyncope, documented sustained ventricular tachycardia or fibrillation, or sleep at 9.1±+11.1 months after implantation. Patients survived 23.8±18.0 months after AICD discharge. Left ventricular dysfunction (p=0.008 for ejection fraction less than 25%) was associated with earlier AICD discharge and shortened survival after AICD discharge (p =0.008 for ejection fraction less than 25%;p=0.01 for New York Heart Association functional class III and IV). ,B-Blocker administration (p=0.006) and coronary bypass surgery (p=0.06) were associated with later AICD discharge. Coronary bypass surgery (p=0.035) but not P-blockers was associated with more prolonged survival after AICD discharge.Conclusions. These data suggest that a relatively easy algorithm can be applied to predict which patient will benefit most from AICD implantation. (Circulation 1991;84:558-566) Automatic implantable cardioverter-defibrillators (AICD) have become an important alternative to conventional treatment of patients with recurrent hypotensive ventricular tachyarrhythmias. Several groups, including our own, have demonstrated effective termination of sustained ventricular tachycardia or fibrillation by this device.1-9 AICD implantation thus far has been largely reserved for cardiac arrest survivors when antiarrhythmic medication is not efficacious. Prolongation of life by this device has not been proven by a prospective, randomized trial because withholding AICD therapy has not been possible because of ethical considerations. Whether survival has been improved by the AICD, therefore, has been the subject of discussion.10 Similarly, factors associated with improved survival or enhanced benefit in patients with the AICD remain unknown.

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