Richard F. Dunn

Exercise-induced ST-segment elevation. Correlation of thallium-201 myocardial perfusion scanning and coronary arteriography.

Exercise-induced ST-segment elevation was correlated with myocardial perfusion abnormalities and coronary artery obstruction in 35 patients. Ten patients (group 1) developed exercise ST elevation in leads without Q waves on the resting ECG. The site of ST elevation corresponded to both a reversible perfusion defect and a severely obstructed coronary artery. Associated ST-segment depression in other leads occurred in seven patients, but only one had a second perfusion defect at the site of ST depression. In three of the 10 patients, abnormal left ventricular wall motion at the site of exercise-induced ST elevation was demonstrated by ventriculography. Twenty-five patients (group 2) developed exercise ST elevation in leads with Q waves on the resting ECG. The site of ST elevation corresponded to severe coronary artery stenosis and a thallium perfusion defect that persisted on the 4-hour scan (constant in 12 patients, decreased in 13). Associated ST depression in other leads occurred in 11 patients and eight (73%) had a second perfusion defect at the site of ST depression. In all 25 patients with previous transmural infarction, abnormal left ventricular wall motion at the site of the Q waves was shown by ventriculography.In patients without previous myocardial infarction, the site of exercise-induced ST-segment elevation indicates the site of severe transient myocardial ischemia, and associated ST depression is usually reciprocal. In patients with Q waves on the resting ECG, exercise ST elevation way be due to peri-infarctional ischemia, abnormal ventricular wall motion or both. Exercise ST-segment depression may be due to a second area of myocardial ischemia rather than being reciprocal to ST elevation.

The phase image: its relationship to patterns of contraction and conduction.

To determine the relationship of phase changes and abnormalities of ventricular contraction and conduction, we performed phase image analysis of blood pool scintigrams in 29 patients. Eleven patients had no evidence of blood pool contraction or ECG conduction abnormalities, four had contraction abnormalities, seven had abnormal conduction and seven had abnormalities of both variables. The phase delay generally related to the degree of contraction abnormality. The mean phase delay in hypokinetic segments differed from that in normokinetic segments in the same patient (p < 0.025), the phase delay of akinetic and dyskinetic segments differed from that in normokinetic segments (p < 0.001) and the phase delay in dyskinetic segments differed from that in akinetic segments (p < 0.005), but there was a significant overlap in the phase delay in normal and hypokinetic segments. Also, in patients with conduction abnormalities, the minimal associated regional phase delay presented a phase dispersion and a pattern of contraction consistent with the pattern of conduction and different from normal. A single study performed both at rest and with stress demonstrated the effect of heart rate on phase assessment and confirmed the independent effects of contraction and conduction on phase delay. Acquisition and analytic methods should add significantly to the resolution of the phase method.

Comparison of thallium-201 scanning in idiopathic dilated cardiomyopathy and severe coronary artery disease.

To determine whether cardiomyopathy could be distinguished from coronary artery disease, we used thallium scanning to study 25 patients with severe left ventricular dysfunction and chronic heart failure. Ten patients had normal coronary arteries and idiopathic cardiomyopathy (ejection fraction 20 ± 5%), and 15 patients had multivessel coronary disease and left ventricular dysfunction (ejection fraction 25 ± 6%). The exercise time and maximal heart rate were similar in the two groups. Two patients with cardiomyopathy and 11 with coronary artery disease had a positive exercise ECG (p < 0.05). Thallium scans showed perfusion defects in all 25 patients. The perfusion defects were complete in nine coronary artery disease patients (60%) and in one patient (10%) with cardiomyopathy (p < 0.05). Extensive defects involving more than 40% of the left ventricular circumference, the number of segments involved, redistribution on the 4-hour scan, lung uptake and ventricular size were similar in the two groups. Perfusion defects on thallium scanning can occur in patients with idiopathic dilated cardiomyopathy and chronic heart failure. Thallium scanning cannot be reliably used in patients with chronic heart failure to distinguish coronary artery disease from cardiomyopathy unless complete defects are present.

Noninvasive prediction of multivessel disease after myocardial infarction.

In 65 patients with a previous transmural myocardial infarction (anterior in 33, inferior in 32), exercise thallium scanning was compared with 12-lead exercise electrocardiography to see if multivessel disease could be detected. At coronary arteriography 40 patients were shown to have multivessel disease (⩾70% diameter stenosis in two or three vessels) and 25 patients had one-vessel disease. On the exercise scan thallium defects corresponding to the electrocardiographic site of infarction were present in all patients. Patients with one-vessel and multivessel disease were separated by exercise-induced angina, perfusion defects on the exercise thallium scan in more than one specific vascular area, and a positive exercise ECG associated with angina, but not by a positive exercise ECG alone. Of the 40 patients with multivessel disease, 85% had defects in more than one vascular area on the thallium scan and 70% had a positive exercise ECG (p = NS). Of the 37 patients with thallium defects in more than one specific vascular area, 92% had multivessel disease, compared with 72% of the 39 patients who had a positive exercise ECG (p < 0.05). Periinfarctional ischemia was present in 38 of the 65 patients (58%) (14 of 25 with one-vessel disease and 24 of 40 with multivessel disease), and did not correlate with the severity of the corresponding coronary artery disease. When thallium defects that resolved were noted in a second vascular area, they were associated with a resolving rather than a constant defect in the vascular area where the infarction had occurred (p < 0.005). In patients after a transmural myocardial infarction, multivessel disease can be better differentiated from one-vessel disease by thallium scanning than by exercise electrocardiography.

Exercise-induced ST-segment elevation in leads V1 or aVL. A predictor of anterior myocardial ischemia and left anterior descending coronary artery disease.

Exercise-induced ST-segment elevation in leads V1 and/or aVL in the absence of anterior Q waves occurred in 46 of 190 patients (24%) who underwent 12-lead exercise electrocardiography with thallium-201 myocardial perfusion imaging and coronary arteriography. Significant left anterior descending coronary artery (LAD) disease was present in 38 of 46 patients (83%) with V1/aVL ST elevation and in 72 of 144 patients (50%) without V1/aVL ST elevation (p < 0.0005). Anterior myocardial ischemia, indicated by reversible anterior perfusion defects on thallium scanning, was present in 40 of 46 patients (87%) with V1/aVL ST elevation and in 25 of 144 patients (17%) without V1/aVL ST elevation (p < 0.0005). Exercise ST elevation in V1/aVL was detected in 38 of 110 of the patients (35%) with LAD disease, for a specificity of 90%, and in 40 of 65 of the patients (62%) with anterior myocardial ischemia, for a specificity of 95%.We conclude that during 12-lead exercise electrocardiography, ST-segment elevation in V1 and/or aVL in the absence of anterior Q waves predicts anterior myocardial ischemia and LAD disease.

Multivessel coronary artery spasm.

A 60-year-old patient with variant angina was shown to have myocardial ischemia in two different regions supplied by separate major coronary arteries. Neither artery had significant coronary atherosclerotic obstruction. Ventricular fibrillation was noted during ST-segment elevation in anteroseptal leads. The attacks of pain and arrhythmias disappeared during nifedipine therapy.

The late prognostic value of acute scintigraphic measurement of myocardial infarction size.

Infarct, perfusion and blood pool scintigraphy were performed in 62 patients during hospitalization for acute myocardial infarction. The largest measured infarct or perfusion image defect and left ventricular ejection fraction were related to the late prognosis determined a mean of 16 months after the event. Breakpoint values for all scintigraphic variables could separate those who were asymptomatic on followup from those who died. The best indicators for selection of survivors and nonsurvivors were a scintigraphic infarct size &phis; 25 cm2 and a perfusion abnormality > 35% of the projected left ventricular area. Among patients with perfusion abnormalities above this limit, 61% died; 93% of those with small perfusion abnormalities survived. Scintigraphic measurements of relative myocardial perfusion and function best separated patients asymptomatic on follow-up from those who developed heart failure and also best identified those with an unfavorable evolution, who developed heart failure or died. Early scintigraphic parameters appeared more accurate than other clinical laboratory indicators for determining late prognosis and could be important in planning treatment after acute infarction.

Coronary artery spasm during exercise: treatment with verapamil.

Six patients who had documented coronary spasm and no coronary artery with organic obstruction > 50% developed angina and ST-segment elevation on exercise testing. Oral verapamil, 160-480 mg/day, prevented exercise-induced ischemia in all patients and increased maximal work capacity from 611 ± 250 kpm to 808 ± 160 kpm (p < 0.02). In two patients, a relationship between the prevention of exercise-provoked ischemia and the plasma concentration of verapamil was demonstrated, and in one of these, the relationship had a diurnal pattern. Patients with variant angina may develop coronary spasm on effort and often respond to verapamil.

A consideration of factors affecting the diagnostic accuracy of thallium-201 myocardial perfusion scintigraphy in detecting coronary artery disease

Several factors influence the ability of TI-201 myocardial perfusion scintigraphy to detect coronary artery disease. Among these are the physiologic effect of the coronary lesion on relative myocardial perfusion and radionuclide distribution; technical and physiologic aspects of the scintigraphic process; and observer interpretation. The diagnostic accuracy of this scintigraphic method is related to: (1) the extent of the hypoperfused myocardium, which will depend on the severity and extent of coronary disease, the presence of collaterals, the exercise method, and the timing of thallium administration and scintigraphy; (2) the scintigraphic process, which depends on the nature of the isotope, the imaging system, and the method of image display; and (3) image interpretation, which depends on the experience of the observer as well as on the area of hypoperfused myocardium and the scintigraphic process. The diagnostic accuracy of scintigraphy for detecting coronary disease can be optimized by computer methods of image enhancement, which maximize differences in image contrast; by electrocardiographic gating; and by emission computer tomography. Other computer methods have been developed to reduce or eliminate observer intervention in interpretation and to increase the objectivity of the method.

Late prognostic value of scintigraphic parameters of acute myocardial infarction size in complicated myocardial infarction without heart failure

Perfusion scintigraphy with thallium-201, infarct scintigraphy with technetium-99m pyrophosphate (TcPYP), and equilibrium blood pool scintigraphy were performed during the initial hospitalization for acute myocardial infarction (MI) in 25 patients without evidence of heart failure who presented with advanced electrocardiographic rhythm and conduction disturbances requiring treatment. Scintigraphic findings during short-term hospitalization were related to the late clinical follow-up performed an average of 14 months later, where patients were grouped as asymptomatic, 8 patients; symptomatic, 9 patients; and deceased, 8 patients. Quantitation of perfusion abnormalities, TcPYP image abnormalities, and left ventricular ejection fraction (EF) revealed that the deceased group had significantly larger TcPYP abnormalities (36 +/- 20 cm2), absolute perfusion abnormalities (32 +/- 16 cm2), and perfusion abnormalities expressed as a percentage of the projected left ventricular area (42 +/- 8%) than the asymptomatic group (13 +/- 8 cm2, 14 +/- 6 cm2, and 20 +/- 9%; p less than 0.05, p greater than 0.05, and p less than 0.01, respectively). The percent perfusion abnormality was significantly larger in the deceased group (42 +/- 8%, p less than 0.01) than in either the symptomatic group (35 +/- 13%, p less than 0.01) or the asymptomatic group (20 +/- 9%), and this parameter in the symptomatic group also differed from that in the asymptomatic group (p less than 0.01). The study indicates that patients with rhythm and conduction disturbances and without congestive heart failure during acute MI may follow an uncomplicated or a complicated late clinical course. Early scintigraphic measurements of MI and perfusion correlate well with this outcome; however, EF could not differentiate among prognostic subgroups.