Comparison of thallium-201 single-photon emission computed tomography and electrocardiographic response during exercise in patients with normal rest electrocardiographic results.

OBJECTIVES: This study compared the diagnostic accuracy of exercise thallium-201 single-photon emission computed tomography (SPECT) with the exercise electrocardiographic (ECG) response in patients with normal baseline ECG results. BACKGROUND: Previous studies comparing exercise thallium imaging with exercise electrocardiography have included patients with abnormal rest ECG results that may have biased the results in favor of thallium imaging. METHODS: Of 321 patients with a pretest likelihood of coronary artery disease of 70 +/- 29% (mean +/- SD) who underwent exercise stress testing and coronary angiography, 68 had no coronary artery disease; 94 had one-vessel disease; 79 had two-vessel disease; and 80 had three-vessel or left main coronary artery disease. RESULTS: The diagnostic accuracy of SPECT was higher than that of the ECG response (79% vs. 49%, p < 0.0001). Patients with extensive (left main or three-vessel) coronary artery disease were older and had a lower work load, lower heart rate, greater ST segment depression and more extensive perfusion abnormalities than patients with no disease or one- or two-vessel disease. Multivariate discriminant analysis of exercise and thallium variables identified multivessel thallium abnormalities (F = 35), exercise heart rate (F = 18) and extent of ST segment depression (F = 6) as independent predictors of extensive disease. Of the 80 patients with left main or three-vessel disease, 37 (46%) had > or = 2-mm ST segment depression, 44 (55%) had multivessel SPECT abnormalities, and 61 (76%) had either > or = 2-mm ST depression or multivessel SPECT abnormalities (p = 0.0005 vs. the ECG response; p = 0.01 vs. SPECT). CONCLUSIONS: In patients with an intermediate to high pretest probability of coronary artery disease and normal baseline ECG results, SPECT is superior to the ECG response in detecting coronary disease. Further, SPECT provides incremental power in identifying patients with extensive (left main or three-vessel) coronary disease.

Independent and incremental prognostic value of exercise thallium single-photon emission computed tomographic imaging in women.

BACKGROUND: This study examined the independent and incremental prognostic value of exercise thallium single-photon emission computed tomographic imaging in 212 women who also underwent coronary angiography. METHODS AND RESULTS: The left ventricular ejection fraction was normal (65% +/- 15%). During a mean follow-up of 40 months, 27 women had events (cardiac death or nonfatal myocardial infarction). Univariate Cox survival analysis showed several variables to be different between patients with events and those without events: age, exercise heart rate, the extent of coronary artery disease, reversible thallium defects, number of segments with reversible abnormality, and size of perfusion abnormality. Multivariate survival analysis showed that a large perfusion abnormality and age were the independent predictors of events. Actuarial life-table analysis showed that women with a large thallium abnormality (> or = 15% of the myocardium) had significantly worse event-free survival rates than had women with no or small abnormalities (Mantel-Cox statistic = 16; p = 0.0001). CONCLUSIONS: Thus exercise thallium-201 single-photon emission computed tomographic imaging provides independent and incremental prognostic information to clinical, exercise, and coronary angiographic results in women. The presence of a larger thallium abnormality identifies women at high risk of cardiac events.

Serial changes in left ventricular function after coronary artery bypass: implications in viability assessment.

Improvement in left ventricular (LV) performance after coronary artery bypass surgery remains the gold standard in myocardial viability assessment. The time-related changes, however, are not well known. This study examined the LV ejection fraction (EF) by gated blood pool imaging early (6 +/- 4 days) and late (62 +/- 24 days) after surgery in patients with normal preoperative EF (group 1, n = 12) and those with LV dysfunction (group 2, n = 15). There were no changes in the clinical status between the early and late studies, and all patients had normal sinus rhythm. Group 1 had no significant change in EF (preoperatively 62%, early postoperatively 64%, late postoperatively 63%; p = NS). In group 2, EF was 26% +/- 8% preoperatively; 30% +/- 10% early postoperatively; and 34% +/- 8% late postoperatively (p < 0.05). Postoperatively there was > or = 5% improvement in EF in 4 patients early and 11 patients late (p < 0.05). Patients who showed early improvement continued to do so in the late study but, additionally, 7 patients showed improvement only in the late study. Thus the timing of EF measurement after surgery is important in patients with LV dysfunction but not in patients with normal LV function. Early assessment may underestimate the prevalence and degree of recovery.

Prognostic implications of normal exercise tomographic thallium images in patients with angiographic evidence of significant coronary artery disease.

This study examines the prognostic implications of normal exercise tomographic thallium images in medically treated patients with angiographic evidence of coronary artery disease (CAD). There were 97 patients aged 60 +/- 10 years; 52 had 1-, 30 had 2-, and 15 had 3-vessel CAD (> or = 50% diameter stenosis). The exercise test was submaximal in 51 patients (53%); ST-segment depression during exercise occurred in 20 patients (21%), and angina during exercise occurred in 23 patients (24%). Most patients (71%) were receiving antianginal therapy. During a mean follow-up of 32 months, only 3 patients had cardiac events: 2 died of cardiac causes and 1 had nonfatal myocardial infarction (event rate 1.1%/year). None of those 3 patients had positive ST response during exercise. Thus, medically treated patients with CAD (including those with multivessel CAD) have a benign prognosis in the presence of normal exercise thallium images. These results have important implications in patient management and cost of health delivery.

The treadmill exercise score revisited: coronary arteriographic and thallium perfusion correlates.

The treadmill exercise score has been used to stratify patients into low-, moderate-, and high-risk groups. This score is derived from ST segment depression, angina, and exercise duration. To determine the coronary arteriographic and exercise thallium perfusion correlates of the score, we examined the extent of coronary artery disease and exercise single photon emission computed thallium-201 results in 834 patients for whom cardiac catheterization data were available. Of those, 174 had no coronary artery disease, 195 had one-vessel, 246 had two-vessel, and 219 had three-vessel disease. Based on the treadmill exercise score, 369 were in the low-risk, 384 in the moderate-risk, and 81 in the high-risk group. The extent of coronary artery disease was 2.1 +/- 1 diseased vessels in the high-risk, 1.7 +/- 1 in the moderate, and 1.4 +/- 1.1 in the low-risk group (p < 0.01). The extent of the thallium abnormality (maximum number of abnormal segments 120/patient) was 10 +/- 6 in the high-risk, 7 +/- 6 in the moderate, and 6 +/- 5 in the low-risk group (p < 0.05). Based on the extent of coronary artery disease and results of thallium imaging, patients were reclassified into three groups: group 1 had three-vessel disease and/or > or = 10 abnormal segments (n = 387), group 3 had no coronary artery disease or one-vessel disease and less than five abnormal segments (n = 212), and the remaining patients were in group 2 (n = 235).(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of intraluminal pressure on hemodynamics and vasoconstriction responses of stenotic arteries.

BACKGROUND: Clinical and morphological studies clearly indicate that most human coronary artery stenoses are capable of vasomotion. Variable ischemic thresholds, ischemia unrelated to work load, and variant angina further show the presence and importance of vasoconstriction in coronary artery stenosis. Despite the importance of vasoconstriction, the effect of intraluminal pressure on the hemodynamic response to vasoconstrictors has not yet been examined. Intraluminal pressure is a primary determinant of vessel size and the force opposing vasoconstriction. Accordingly, we examined the effects of intraluminal pressure on the hemodynamic response to norepinephrine (NE)-induced vasoconstriction. METHODS AND RESULTS: In canine carotid arteries perfused with physiological salt solution, pressures at the proximal and distal ends of the artery, as well as flow, were continuously recorded. We altered intraluminal pressure using three diverse interventions: changes in perfusion pressure, decreasing distal resistance, and collaterals. In normal, nonstenotic arteries, NE decreased the external vessel diameter but did not reduce flow. Perfusion pressure changes did not affect the ED50 of the NE-diameter relation. After an intraluminal stenosis was created, NE-induced constriction decreased flow. The threshold concentration of NE needed to decrease flow decreased as the perfusion pressure decreased (38.5 +/- 17.9, 2.3 +/- 1.3, and 0.12 +/- 0.1 x 10(-7) mol/l for 125, 100, and 75 mm Hg of perfusion pressure, respectively; p less than 0.05). Lowering distal resistance decreased stenotic pressure and decreased the threshold NE concentration from 5.4 +/- 1.9 to 0.34 +/- 0.2 x 10(-7) mol/l (p less than 0.05), and increasing stenotic pressure with collaterals increased the threshold NE concentration from 2.6 +/- 1.4 to 7.5 +/- 4.6 x 10(-7) mol/l (p less than 0.05). CONCLUSIONS: In stenotic arteries, interventions that lowered the intraluminal pressure decreased the threshold NE concentration needed to decrease flow, and interventions that raised the intraluminal pressure increased the threshold NE concentration. This pressure-dependent constrictor sensitivity affects the vasomotor tone and is important in pathophysiology of ischemia occurring with hypotension (low perfusion pressure) or mild increase in myocardial oxygen demand (low distal arteriolar resistance). The results also suggest that collaterals, by maintaining stenotic pressure, could decrease the constrictor sensitivity and prevent ischemia.

Utilization of screening mammography: comparison of different physician specialties.

Data obtained on 426 consecutive patients referred to a breast center by 122 physicians, including family practitioners, general surgeons, and other specialists, showed that the obstetricians-gynecologists referred the greatest average number of patients per physician, with more than 50% of these referrals for screening mammography. Internists referred fewer patients by nearly a factor of ten, with only one-third of these patients referred for screening mammography. Internists may be the weakest link in the utilization of screening mammography.