Improvement of myocardial perfusion and left ventricular function after coronary artery bypass grafting in patients with unstable angina

Postoperative Dipping Patterns of Mean Arterial Pressure and Mortality After Coronary Artery Bypass Grafting

Blood pressure dipping patterns have long been considered to be associated with adverse events. We aimed to investigate whether dipping patterns of postoperative MAP were related to 90-day and hospital mortality in patients undergoing CABG. Four thousand three hundred ninety-one patients were classified into extreme dippers (night-to-day ratio of MAP ≤ 0.8), dippers (0.8 < night-to-day ratio of MAP ≤ 0.9), non-dippers (0.9 < night-to-day ratio of MAP ≤ 1), and reverse dippers (> 1). Compared with non-dippers, reverse dippers were at a higher risk of 90-day mortality (aHR = 1.58; 95% CI, 1.10-2.27) and hospital mortality (aOR = 1.97; 95% CI, 1.12-3.47). A significant interaction was observed between hypertension and dipping patterns (P for interaction = 0.02), with a significant increased risk of 90-day mortality in non-hypertensive reverse dippers (aHR = 1.90; 95% CI, 1.17-3.07) but not in hypertensive reverse dippers (aHR = 1.26; 95% CI, 0.73-2.19).

Effects of surgery for postinfarction ventricular tachycardia on parameters of left ventricular function

Heart failure is the leading cause of death in patients after surgery for ventricular tachycardia. This study examines the effects of antiarrhythmic surgery on 4 parameters of left ventricular (LV) function. Global ejection fraction, segmental wall motion score, homogeneity of contraction, and diastolic function were measured in 32 patients by technetium-99m radionuclide ventriculography. Ejection fraction was measured from the left anterior oblique image. Wall motion score was assessed semiquantitatively for 11 LV segments from 3 projections. Homogeneity of contraction was expressed as the SD of the LV phase analysis curve during systole from the left anterior oblique image. Diastolic function was expressed in terms of peak and mean first time derivative of the action potential (dV/dt) of the LV function curve. Subgroup analyses were performed to distinguish the effects of aneurysmectomy, coronary artery bypass grafting, and changes in angiotensin converting enzyme inhibitor therapy. Mean systolic function improved after surgery (ejection fraction 22% vs 32%, p <0001; wall motion score 20 vs 13, p <0.0001; phase analysis 18 vs 12, p <0.03). Mean diastolic function also improved (peak dV/dt 0.83 +/- 0.32 vs 1.49 +/- 0.39, p = 0.006; mean dV/dt 0.41 +/- 0.15 vs 0.76 +/- 0.27, p = 0.006). Improvements were not confined to those who had aneurysmectomy or coronary bypass grafting and were not explained by changes in vasodilator therapy. Thus, antiarrhythmic surgery does not inherently damage LV function. Significant improvements were observed in most patients. Failure to improve indicated a poor longer term prognosis.

Basic and clinical aspects of myocardial stunning

Although the pathogenesis of myocardial stunning has not been definitively established, the two major hypotheses are that it is caused by the generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile filaments to calcium. These hypotheses are not mutually exclusive and are likely to represent different facets of the same pathophysiological cascade. For example, a burst of free radical generation after reperfusion could alter contractile filaments in a manner that renders them less responsive to calcium. Increased free radical formation could also cause cellular calcium overload, which would damage the contractile apparatus of the myocytes. There is now considerable evidence that myocardial stunning occurs clinically in various situations in which the heart is exposed to transient ischemia, such as unstable angina, acute myocardial infarction with early reperfusion, exercise-induced ischemia, cardiac surgery, and cardiac transplantation. Recognition of myocardial stunning is clinically important and may impact patient treatment. Although no ideal diagnostic technique for myocardial stunning has yet been developed, thallium-201 scintigraphy or dobutamine echocardiography are available and can be useful to identify viable myocardium with reversible wall motion abnormalities. An intriguing possibility is that so-called chronic hibernation may in fact be the result of repetitive episodes of stunning, which have a cumulative effect and cause protracted postischemic left ventricular dysfunction. A better understanding of myocardial stunning will expand our knowledge of the pathophysiology of myocardial ischemia and provide a rationale for developing new therapeutic strategies designed to prevent postischemic dysfunction.

Combination of dobutamine and myocardial contrast echocardiography to differentiate postischemic from infarcted myocardium

OBJECTIVES

This study tested whether the combination of dobutamine echocardiography (DE) and myocardial contrast echocardiography (MCE) was superior to either technique alone in identifying postischemic myocardium and in differentiating it from necrotic myocardium.

BACKGROUND

Wall motion abnormalities at rest occur in postischemic myocardium in the presence of infarction, stunning or hibernation, alone or in combination. Various investigators have suggested that either DE or MCE can be used to identify the presence of myocardial viability.

METHODS

We studied a total of 53 mongrel dogs in an open chest model of coronary occlusion of various durations followed by reperfusion and dobutamine administration (10 microg/kg body weight per min). MCE with aortic root injections of Albunex (area under the curve) and DE (percent thickening fraction) were performed at the different stages. Postmortem triphenyltetrazolium chloride (TTC) staining was used to identify myocardial necrosis.

RESULTS

Thirteen dogs underwent brief (15 min) occlusions and developed no necrosis (Group I). Of 40 dogs that underwent prolonged (30 to 360 min) occlusions, 14 had no infarction (Group II), whereas 26 did (Group III: 12 papillary muscle, 7 subendocardial, 7 transmural). MCE (expressed as percent change from baseline) demonstrated changes that paralleled the blood flow changes observed by radiolabeled microspheres at all interventions (r = 0.67, p < 0.0001). Regional ventricular function improved with dobutamine administration in the ischemic region in all three groups. The sensitivity (88%) for detecting myocardial viability was superior when the two techniques were combined; however, a poor specificity (61%) was observed.

CONCLUSIONS

Contractile reserve and perfusion data are complementary when assessing regional wall motion abnormalities in postischemic myocardium. DE alone cannot differentiate postischemic from infarcted myocardium; simultaneous data on myocardial perfusion are required. The combination of DE and MCE is superior to either technique alone for identifying the absence of myocardial necrosis.

Changes in wall motion in patients treated for unstable angina. A suggestion of the stunned and hibernating myocardium in humans. UNASEM Collaborative Study Group. Unstable Angina Study Using Eminase

BACKGROUND

A double-blind, placebo-controlled study using anistreplase was performed in 159 patients with unstable angina. All patients had a history of unstable angina combined with typical ECG changes and without evidence of a previous, recent, or ongoing myocardial infarction. The purpose of the present study was to analyze the relationship between the patency of the culprit artery and the behavior of the ischemia-related regional left ventricular (LV) wall motion.

METHODS AND RESULTS

On entry to the study, all patients received conventional drug therapy: i.v. nitroglycerin therapy, an oral beta-blocking agent, and a calcium antagonist. Baseline angiography was carried out within 3 h after randomization, a mean of 4.2 +/- 3.0 h (range, 1 to 17 h) after the last attack of chest pain. Treatment with trial medication was withheld in 33 cases. Sixty-five patients with coronary artery disease received anistreplase (30 U/5 min)/heparin and 61 patients heparin-only therapy. Angiography was repeated 20.6 +/- 4.6 h (mean +/- SD; range, 12 to 39 h) after the baseline angiographic study. To assess changes in regional myocardial wall motion, the LV wall was divided into seven segments. The ischemia-related coronary artery stenosis was calculated quantitatively and related to the quantitatively assessed mean regional left ventricular ejection fraction (RLVEF) of the ischemia-related segments. In 118 of 126 patients who received trial medication, we found that anistreplase/heparin therapy leads to a significantly (p < 0.01) greater reduction in coronary artery diameter stenosis than heparin-only therapy (n = 63, mean +/- SD, 11 +/- 22, vs n = 55, mean +/- SD, 3 +/- 11%). Anistreplase/heparin therapy was related to a larger significant improvement of the ischemia-related RLVEF than heparin-only therapy, although the latter association was not statistically significant (n = 63, mean +/- SD, 7 +/- 15, vs n = 55, mean +/- SD, 5 +/- 14%). The effects of change of coronary artery stenosis on regional LV wall motion were also determined. A paradoxical finding was that a persistently occluded vessel or a vessel showing an increase in coronary artery stenosis was associated with a greater improvement of the ischemia-related RLVEF than a reopened vessel or a vessel with a reduction in coronary artery stenosis (n = 15, mean +/- SD, 7 +/- 11, vs n = 41, mean +/- SD, 8 +/- 13, vs n = 15, mean +/- SD, 1 +/- 12, vs n = 47, mean +/- SD, 5 +/- 16%, NS). One day after the last attack of chest pain, the regional LV wall motion was still abnormal in about 20% of patients.

CONCLUSION

In these patients with unstable angina, the LV wall motion improved both in the treated and the control group at follow-up angiography 1 day later. Improved coronary arterial anatomy was associated with a lesser improvement of the LV contractile function than when worsening of the coronary angiographic appearance occurred. There is no rational explanation of these results. This is a beginning of an effort to elucidate the clinical significance of the stunned and hibernating myocardium in humans.

Comparative study of left ventricular function in patients with unstable angina, non-Q wave myocardial infarction and stable angina pectoris: assessment with atrial pacing and digital ventriculography

To compare left ventricular global and segmental function at rest and during right atrial pacing in patients with unstable angina, non-Q wave myocardial infarction, and stable angina (class III angina), low-dose digital subtraction ventriculography was performed at rest and after abrupt cessation of pacing in 42 patients with unstable angina, 8 patients with non-Q wave myocardial infarction and 15 patients with stable angina during selective coronary arteriography. Left ventricular ejection fraction was significantly lower at rest in patients with unstable angina (P < 0.01) and non-Q wave myocardial infarction (P < 0.05) and during pacing (P < 0.01). These two groups of patients had significantly higher values of left ventricular end-diastolic and end-systolic volumes at rest and during pacing as compared with stable angina group. In comparing various clinical patterns of unstable angina, ejection fraction was significantly (P < 0.05) lower during pacing in patients with crescendo angina than in new-onset angina. However, ejection fraction was significantly (P < 0.01) lower in crescendo angina only at rest as compared with rest angina. The length of zone of severe hypokinesia was greater in unstable angina (P < 0.01) as well as in non-Q wave myocardial infarction (P < 0.05) both at rest and during pacing as compared with stable angina. Contractility of region of hypokinesia during pacing was higher (P < 0.01) in stable angina than in unstable angina and non-Q wave myocardial infarction. In analyzing segmental function in various subgroups of unstable angina, the authors found that the length of total hypokinesia was significantly higher (P < 0.05) during pacing in crescendo angina than in new-onset angina. Contractility of region of hypokinesia was lowest at rest and during pacing in patients with crescendo angina. This study demonstrates that patients with unstable angina as well as non-Q wave myocardial infarction were characterized by more pronounced global and segmental left ventricular dysfunction at rest and during pacing as compared with patients with stable angina, which may explain the poorer prognosis in the former two groups. This study also shows that patients with crescendo angina have more profound left ventricular global and regional dysfunction as compared with patients with new-onset as well as rest angina.

Low-dose dobutamine echocardiography predicts the early response of dysfunctioning myocardial segments to coronary artery bypass grafting

Dobutamine echocardiography has recently been introduced for use in identification of viable myocardium in patients with acute myocardial infarction and prediction of the response of dysfunctioning myocardial segments to coronary angioplasty. The aim of this study was to evaluate whether this test may be used to predict the early response of dysfunctioning myocardial segments to surgical revascularization. We studied 30 patients with three-vessel disease and chronic, stable angina pectoris during coronary artery bypass grafting (CABG). Patients were monitored by intraoperative transesophageal echocardiography in the transgastric short-axis view at the papillary muscle level. The left ventricle was divided into eight segments; and 240 myocardial segments were analyzed. Percentage of systolic wall thickening (PSWT) was calculated in each segment at baseline (early after pericardiectomy), before bypass during dobutamine infusion (5 micrograms/kg/min), and after separation from cardiopulmonary bypass. Segments showing PSWT < 30% at baseline were considered dysfunctional. Segments showing an increase in PSWT > 10% during dobutamine infusion were considered responders. Segments showing an increase in PSWT < 10% during dobutamine infusion were considered nonresponders. At baseline, 161 (67%) of 240 segments had PSWT < 30% (dysfunctioning segments). During dobutamine, 98 (60%) of these segments increased PSWT > 10% (from 11.3% +/- 7.6% to 24.2% +/- 12.0%, p < 0.01; responder segments), and 63 (40%) increased PSWT < 10% (from 10.2% +/- 4.9% to 8.3% +/- 5.5%, p value not significant [NS]; nonresponder segments).(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged wall motion abnormalities after chest pain at rest in patients with unstable angina: a possible manifestation of myocardial stunning

Although myocardial "stunning" would be expected to occur in unstable angina, there is no published report in which the recovery of regional left ventricular function was serially monitored in this syndrome. To determine whether the time course of the regional wall motion abnormalities associated with unstable angina is consistent with myocardial stunning, 20 consecutive patients with unstable angina were studied prospectively. Regional left ventricular wall motion was assessed by two-dimensional echocardiography during or immediately after angina at rest and at serial times thereafter. Six of the 20 patients fulfilled the inclusion criteria. The recovery of segmental wall motion after chest pain was consistently found to be delayed in all six patients, but a considerable variability was observed. In at least two subjects, the improvement was rapid and the wall motion abnormalities disappeared almost completely within 2 hours after the chest pain. Both of these patients had the shortest duration of angina (approximately 10 minutes). In contrast, in three other patients with longer duration of chest pain, the improvement was slower and significant wall motion abnormalities were still present at 24 hours after the chest pain. In five control patients who had angiographically-documented coronary artery disease but no recent episode of angina, there was no significant change in segmental wall motion during a period of observation equivalent to that used in the unstable angina group. This study evaluated for the first time the time course of wall motion abnormalities in patients with unstable angina. The results demonstrate that angina at rest is followed by a prolonged depression of contractile function, which may persist for up to 24 hours or even longer. Because none of the patients had evidence of acute myocardial infarction or recurrent ischemia, our observations suggest myocardial stunning as the pathophysiologic substrate for the slow recovery of wall motion. The present results are consistent with the concept that myocardial stunning does occur in unstable angina and indeed may be a component of the natural history of this disorder; however, further investigations using simultaneous measurements of function and flow will be necessary to unequivocally distinguish myocardial stunning from hibernation and silent ischemia.

Frequency and predictors of left ventricular segmental dysfunction in patients with recent rest angina

The relation between coronary artery lesion morphology and associated segmental left ventricular (LV) dysfunction in patients with unstable angina is unclear. Fifty-two patients with angina occurring at rest who underwent cardiac catheterization within 3 days of the last episode of pain and had no enzymatic evidence for myocardial necrosis were evaluated. Coronary artery narrowings deemed responsible for the ischemic episodes were analyzed with regard to the artery involved, maximal diameter of the narrowing, presence of thrombus, and complex appearance. Time to catheterization, age, sex and electrocardiographic evidence of ischemia were also noted. Segmental LV dysfunction in the territory supplied by the "culprit lesion" was present in 58% of patients. It occurred significantly more often with lesion location in the left anterior descending coronary artery, and was less frequent with lesions in the left circumflex and ramus coronary arteries. Ischemic electrocardiographic changes were more sensitive in predicting LV dysfunction with culprit lesion location in the left anterior descending or right coronary artery. LV dysfunction could not be predicted by any other parameter analyzed. It is concluded that postischemic LV dysfunction occurs frequently in rest angina, especially when the severest narrowing is in the left anterior descending coronary artery.

Clinical relevance of myocardial "stunning"

Experimental studies have demonstrated that myocardium reperfused after reversible ischemia exhibits prolonged depression of contractile function ("stunning"). Despite the multiplicity of clinical situations in which myocardial stunning would be expected to occur, investigation of this phenomenon in humans has been hindered by several major problems, including the limited accuracy of the methods available to measure regional left ventricular function, the inability to quantify regional myocardial blood flow during acute ischemia, the difficulty in establishing with certainty, the beginning and end of an ischemic episode, and the uncontrolled influence of variables (such as preload, afterload, adrenergic tone, and inotropic therapy) that have a major impact on postischemic dysfunction. The main problem is to discern whether a reversible defect of contractility is caused by stunning, silent ischemia, or hibernation (i.e., chronic ischemia). This differential diagnosis requires the simultaneous measurement of regional myocardial function and flow, which thus far has not been generally possible. Despite these limitations, however, numerous clinical observations suggest that stunning does occur in various settings in which the myocardium is exposed to transient ischemia, including coronary angioplasty, exercise-induced angina, angina at rest (unstable or variant), acute myocardial infarction with early reperfusion, open-heart surgery, and cardiac transplantation. Recognition of this entity is important, amongst other reasons, because it is likely to cause significant morbidity and because it is potentially correctable with inotropic therapy or even preventable with antioxidant therapy. In addition, the appreciation of the phenomenon of myocardial stunning should allow the clinician to assess the efficacy of reperfusion therapy with greater accuracy and to recognize that patients should not be denied mechanical revascularization solely because of an abnormal left ventricular wall motion. Perhaps the most intriguing clinical implication of the concept of myocardial stunning is the possibility that in patients who exhibit frequent episodes of ischemia in the same territory, the myocardium may not be able to fully recover between episodes and thus may remain reversibly depressed for prolonged periods of time, or even chronically, which could account for some cases of "ischemic cardiomyopathy." Our understanding of myocardial stunning in humans is still relatively crude and will not significantly improve until studies are performed that measure simultaneously regional myocardial perfusion and function (so that stunning can be differentiated from silent ischemia and hibernation). Future important areas of research should also include the elucidation of whether stunning can become chronic and the evaluation of therapies (such as antioxidant treatments) designed to prevent this contractile abnormality.(ABSTRACT TRUNCATED AT 400 WORDS)

Reversal of segmental hypokinesis by coronary angioplasty in patients with unstable angina, persistent T wave inversion, and left anterior descending coronary artery stenosis. Additional evidence for myocardial stunning in humans

To evaluate the significance of persistent negative T waves during severe ischemia, we prospectively studied 62 patients admitted for unstable angina without evidence of recent or ongoing myocardial infarction. A critical stenosis on the left anterior descending coronary artery (LAD), considered as the culprit lesion, was successfully treated by percutaneous transluminal coronary angioplasty (PTCA). The patients were divided into two groups according to the admission electrocardiogram: T NEG group (n = 32) had persistent negative T waves, and the T POS group (n = 30) had normal positive T waves on precordial leads. The two groups had similar baseline clinical, hemodynamic, and angiographic characteristics. All patients underwent a complete clinical and angiographic evaluation (coronary arteriography and left ventriculography) before undergoing PTCA and 8 +/- 3 months later. Left ventricular anterior wall motion was evaluated by the percent shortening of three areas (S1, S2, and S3) considered as LAD-related segments on left ventriculograms. Before PTCA, there was no significant difference in global ejection fraction between the two groups despite a significant depression in anterior mean percent area shortening in the T NEG compared with the T POS group (S1, 44 versus 54, p less than 0.01; S2, 39 versus 48, p less than 0.01; S3, 44 versus 50, NS). At repeated angiography, the anterior mean percent area shortening improved significantly in the T NEG group (S1, from 44 to 61, p less than 0.001; S2, from 39 to 58, p less than 0.001; S3, from 44 to 61, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Changing concepts in the pathophysiology of myocardial ischemia

The principal common pathway for myocardial ischemia is an oxygen supply-demand imbalance; more recently, greater emphasis has been placed on limitations of myocardial blood supply, as well as excessive myocardial oxygen demand. Myocardial ischemia is a metabolic event resulting from inadequate oxygen delivery to local tissues. The physiologic effects of ischemia are observed through abnormalities in left ventricular function, electrocardiographic changes, and often, by angina pectoris. Prognostic and therapeutic outcomes are significantly related to the pathophysiology of the underlying coronary lesion. Because myocardial ischemia often occurs without symptoms, clinical distinctions based on angina stability may more appropriately be represented by stable or unstable ischemic syndromes that incorporate silent ischemia. Stable ischemic syndromes occur secondary to coronary plaques, whereas unstable syndromes are the result of active lesions caused by plaque rupture with local thrombus and vasoreactivity that produce intermittent critical decreases in coronary supply. The prognosis of patients with stable ischemia is related to the extent of myocardium at jeopardy and overall left ventricular function. In contrast, unstable syndromes are associated with a worse short-term prognosis, which may be predictable by the presence of silent ischemia or left ventricular dysfunction or both. Therapeutic decisions based on an improved pathophysiologic understanding of ischemic mechanisms as well as the physiologic impact of therapy on cardiac function can enhance efficacy while avoiding adverse effects. Calcium channel blockers appear to afford certain advantages in the treatment of myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute changes in global and regional rest left ventricular function after successful coronary angioplasty: comparative results in stable and unstable angina

The immediate effects of successful percutaneous transluminal coronary angioplasty on global and regional left ventricular function were assessed by comparing 30 degrees right anterior oblique left ventricular angiograms performed immediately before and after angioplasty on 39 patients undergoing 42 successful procedures. Mean (+/- SD) lesion stenosis decreased from 88 +/- 10% to 35 +/- 11% (p less than or equal to 0.001), whereas left ventricular ejection fraction increased from 57 +/- 11% to 64 +/- 10% (p less than or equal to 0.001) for the entire group. Left ventricular functional changes were further subgrouped according to stability of angina. Eighteen procedures were performed on 17 patients with stable angina: 24 procedures were performed on 22 patients with unstable angina defined as angina at rest or on minimal activity or recently accelerated angina. There were no significant subgroup differences in mean age, gender ratio, vessel anatomy, drug therapy or extent of coronary stenosis before or after angioplasty. Global ejection fraction increased significantly for the unstable group (from 54 +/- 11% to 66 +/- 9%, p less than or equal to 0.001) but was unchanged for the stable group (from 61 +/- 9% to 61 +/- 11%, p = NS). In unstable angina, regional ejection fraction (segmental area method) increased for both jeopardized (from 37 +/- 11% to 52 +/- 9%, p less than or equal to 0.001) and nonjeopardized myocardial segments (from 43 +/- 13% to 51 +/- 13%, p less than or equal to 0.001), but improvement was significantly (p less than or equal to 0.02) greater in jeopardized segments.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of coronary artery bypass grafting on left ventricular systolic function at rest: evidence for preoperative subclinical myocardial ischemia

Successful coronary artery bypass grafting (CABG) improves exercise-induced left ventricular (LV) dysfunction in patients with coronary artery disease (CAD), but its potential for improving resting LV function remains controversial. To assess the influence of CABG on LV function at rest, 31 CAD patients without previous myocardial infarction were studied before and 6 months after CABG by radionuclide angiography after all cardiac medicines were withdrawn. No patient had angina or ischemic electrocardiographic changes at rest. In 27 patients with patent bypass grafts, CABG significantly increased LV ejection fraction during exercise (47 +/- 11% before to 63 +/- 9% after operation, p less than 0.001), indicating reduction in exercise-induced LV ischemia. Moreover, LV ejection fraction at rest also increased (55 +/- 9 to 60 +/- 8%, p less than 0.001), with 20 of 27 patients manifesting an increase compared with preoperative values. Eleven of these 20 patients had apparently normal LV function at rest (ejection fraction and regional wall motion) before CABG. LV regional ejection fraction was computed by dividing the LV region of interest into 20 sectors. Regional analysis indicated that improved ejection fraction at rest after CABG occurred in regions developing ischemia during exercise before CABG. In 4 patients with occluded grafts, the ejection fraction at rest was unchanged by CABG globally (59 +/- 8 to 58 +/- 9%, difference not significant) and regionally. Thus, LV global and regional function at rest improved after successful CABG, even in patients with normal global LV ejection fraction and no visually detectable wall motion abnormality before surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

An ischemic index from the electrocardiogram to select patients with low left ventricular ejection fraction for coronary artery bypass grafting

Patients who have a decreased left ventricular (LV) ejection fraction (EF) may be denied coronary by-pass grafting (CABG) because it is assumed that improvement in function is unlikely. If the low LVEF were due to myocardial necrosis, this assumption would be valid. If the dysfunction were due to both necrosis and ischemia, however, then improvement may be possible with CABG. A method capable of identifying such patients would be useful. In this study, an "ischemic index" was determined for 37 patients based on the difference between the presurgical LVEF estimated from the standard 12-lead electrocardiogram by the Selvester QRS score (indicating the extent of dysfunction due to necrosis) and the presurgical LVEF measured from resting multigated radionuclide angiography (indicating dysfunction due to both necrosis and ischemia). It was hypothesized that a high ischemia index, that is, a large discrepancy between estimated and measured LVEF, would be associated with an improved post-surgical measured LVEF. The results showed that patients with an ischemic index of less than or equal to 0 had a mean decrease in LVEF of 8% (p = 0.02) and those with an index between 0 and 10 had no mean change. Patients with an index greater than or equal to 11, however, had a mean increase of 5% (p = 0.02), suggesting that depressed LVEF may improve following CABG among patients whose low function is due primarily to reversible ischemia as indicated by a high ischemic index.

Effects of successful percutaneous transluminal coronary angioplasty on global and regional left ventricular function in unstable angina pectoris

Sixty-eight patients (58 men, 10 women, mean age 56.3 years, range 31 to 72) with unstable angina pectoris, either initially stabilized with or refractory to optimal pharmacologic treatment, were studied to determine whether regional dysfunction due to stunning of the myocardium caused by attacks of chest pain at rest could be improved with percutaneous transluminal coronary angioplasty (PTCA). Patients were included in the study if they had successful 1-vessel PTCA, no angiographic restenosis, no reocclusion or late myocardial infarction and 2 serial left ventriculograms of sufficient quality to allow automated contour analysis before and after PTCA. Global ejection fraction increased significantly (from 56% to 60%, p less than 0.05) only after successful dilatation of a stenosis of the left anterior descending coronary artery. Analysis of regional wall displacement showed significant improvement of regional wall motion in the areas supplied by the dilated vessel of either the left anterior descending, the left circumflex or the right coronary artery. Thus, regional myocardial dysfunction due to stunning of the myocardium in patients with unstable angina improves after successful PTCA.

Effects of coronary artery revascularization and perioperative myocardial infarction on left ventricular wall motion

The effects of coronary artery revascularization and perioperative myocardial infarction on left ventricular wall motion are still controversial. In this study perioperative myocardial infarction was quantitatively estimated with the cumulative activity of the CK-MB isoenzyme in the perioperative period in a group of 77 consecutive patients undergoing coronary artery bypass surgery. After the operation (on average 9 +/- 1.8 months) all the patients were submitted to left ventricular and coronary angiography. Overall the global left ventricular ejection fraction was unchanged after the operation. The subgroup of patients with all patent grafts showed an improvement of both regional wall motion (P less than 0.05) and ejection fraction (from 58 +/- 13 to 64 +/- 13%, P less than 0.005); the number of angiographically abnormal left ventricular segments decreased from 28.5 to 16.6% (P less than 0.001). The cumulative activity of CK-MB enzyme was significantly correlated with the pre- and postoperative changes of ejection fraction (r = -0.51, P less than 0.01). Thus coronary artery bypass surgery can improve regional wall motion, but the likely benefit is observed in the absence of a perioperative myocardial ischemic damage.

Reversal of rest myocardial asynergy during exercise: a radionuclide scintigraphic study

While exercise-induced segmental left ventricular wall motion abnormalities are well described, the phenomenon of improvement in certain asynergic segments during exercise in some patients remains a curiosity. To assess this unexpected finding, results were analyzed in 85 patients with wall motion abnormalities at rest who underwent two view (45 degrees left anterior oblique and anterior) exercise radionuclide ventriculography and exercise thallium-201 myocardial perfusion imaging. Wall motion was scored with a 5 point system (from 3 [normal] to - 1 [dyskinesia]); normalization or increase of 2 or more points with exercise signified improvement. Forty-eight patients (56%) had no change or further deterioration of wall motion at peak exercise, 15 (18%) showed both improvement of wall motion and deterioration and 22 (26%) showed only improvement of wall motion. Wall motion improvement during exercise was found in 57 (20%) of 279 segments with asynergy at rest. Of these 57 segments improving with exercise, 45 (79%) showed mild and 12 (21%) showed severe asynergy at rest. Only seven segments (12%) were associated with pathologic Q waves. Thallium-201 perfusion was normal in 44 segments (77%) while only 6 segments (11%) had reversible and only 7 (12%) had nonreversible thallium-201 defects.

IN CONCLUSION

1) wall motion that is abnormal at rest can sometimes improve with exercise; 2) this phenomenon generally occurs in zones without a Q wave or nonreversible thallium-201 defect. Hence, segments with abnormal wall motion at rest that show improvement with exercise appear to represent viable nonischemic segments.

Myocardial perfusion after aortocoronary bypass surgery: measurements at rest and after administration of isoproterenol

This study examined quantitative regional myocardial perfusion (RMP) measured by the washout of 133Xe at rest and after an isoproterenol challenge in 50 patients (group I) studied 8 to 14 days after they underwent saphenous vein bypass grafting to the left coronary artery, and compared this with RMP measured in the native left coronary artery in 14 patients (group II) with significant coronary artery disease and in 12 normal subjects (group III). The double product of the heart rate and aortic systolic pressure was used as an indicator of demand. The statistical significance of group comparisons was analyzed with Dunn's multiple comparisons among means test. Analysis of the data showed no significant difference among the groups with respect to aortic systolic pressure. In subjects at rest, heart rate was lower in groups II and III than in group I, and double product was lower in group II than in group I. After isoproterenol, both heart rate and double product were lower in group II compared with groups I and III, but there was no significant difference between groups I and III with respect to heart rate or double product. Mean resting RMP in group II was lower than in group I; however, results of other group comparisons were insignificant for resting parameters. After isoproterenol, mean flow (ml/100 g/min) in group I was similar to flow in group III (130 +/- 24 vs 139 +/- 26). In contrast, the average flow response after isoproterenol was significantly less in group II when compared with that in group I (105 +/- 20 vs 130 +/- 24) and with that in group III (105 +/- 20 vs 139 +/- 26). Because of differences in levels of demand with isoproterenol, the change in flow was normalized to the percent increase in double product. These data showed results similar to those above, i.e., normalized RMP in patients with coronary artery disease was significantly lower than that in normal subjects (82 +/- 41 vs 119 +/- 57) and in revascularized patients (82 +/- 41 vs 105 +/- 54). However, there was no significant difference between normal subjects and patients who had undergone surgery. To further evaluate the relationship of flow response to demand parameters, we plotted RMP/double product vs resistance. The data revealed a significant correlation between these variables in all groups both in subjects at rest and after isoproterenol.(ABSTRACT TRUNCATED AT 400 WORDS)

Multivariate analysis of angiographic, histologic, and electrocardiographic data in patients with coronary heart disease

In 61 consecutive patients undergoing aortocoronary bypass grafting, angiographic and electrocardiographic (ECG) changes were studied. Histologic delineation of myocardium was obtained by analysis of transmural biopsy specimens acquired at the time of surgery. The use of principal-component analysis revealed three definite groups of patients. Group I comprised patients with histologic findings associated with severe left anterior descending coronary artery (LAD) stenosis, without abnormal wall motion or ejection fraction. ECG abnormalities were limited to ST changes. Group II comprised patients with severe myocardial cell degeneration with only modest fibrosis associated with severe LAD stenosis and severely impaired wall motion. The incidence of infarction on the ECG was low. Group III patients had important myocardial cell degeneration with severe fibrosis associated with severe LAD stenosis, severely depressed wall motion, and significantly impaired ejection fraction. In this group there was a high incidence of infarction apparent on the ECG. Postoperative follow-up (24 months) showed a total survival of 94.4% in group I, 92.8% in group II, and only 72.7% in group III. This identification of subtypes of coronary artery disease seems to be helpful in estimating patient prognosis after coronary surgery.

Improved regional ventricular function after successful surgical revascularization

Left ventricular segments with reversible asynergy at rest demonstrate reversible myocardial perfusion defects on exercise thallium-201 scintigrams. To determine if improved perfusion eliminates asynergy at rest, 23 patients with angina (stable in 21, unstable in 2) were studied before and after coronary artery bypass surgery. All patients underwent exercise myocardial perfusion scintigraphy, contrast ventriculography and coronary arteriography before and after surgery. Selective graft angiography was performed during the postoperative catheterization to determine graft patency. Segmental ventricular function was quantitated by a regional fraction method. The scintigrams were divided into five regions and compared with the corresponding regions of the ventriculogram. Seventy-one of a possible 142 ventricular segments exhibited exercise-induced perfusion deficits. Preoperative regional ejection fraction was normal in 42 of these segments and abnormal in 29. Postoperatively, in 19 of the abnormal segments, function improved or normalized. All these segments had improved perfusion during exercise after surgery and were supplied by a patent bypass graft. Nine of the 10 segments in which abnormal wall motion persisted postoperatively continued to have exercise-induced perfusion deficits, and 9 of the 10 segments were supplied by an occluded or stenotic graft or one with poor run off. Of the 42 segments with normal wall motion preoperatively, 30 had improved perfusion after surgery and 35 maintained normal function. This study indicates that asynergy at rest is permanently reversed after coronary bypass surgery if improved myocardial perfusion can be documented. These findings are consistent with but do not prove the concept that reversible rest asynergy may reflect chronic ischemia or a prolonged effect from previous ischemic episodes.

Percutaneous transluminal coronary angioplasty in patients with stable and unstable angina pectoris: analysis of early and late results

Percutaneous transluminal coronary angioplasty (PTCA) was performed in 50 patients with stable and in 50 patients with unstable angina pectoris, each patient showing an isolated stenosis of more than 80% of the cross-sectional area of a single coronary artery. The technical success rate was 66% in the stable groups (26 of 37 patients [70%] with left anterior descending artery [LAD], 7 of 12 patients [58%] with right coronary artery [RCA]) and 74% in the unstable group (27 of 34 patients [79%] with LAD, 10 of 15 patients [67%] with (RCA). The increase in stenotic area in the unstable group exceeding that in the stable group for LAD stenoses (41.5 +/- 15.1% vs 32.3 +/- 14.5%, p less than 0.03), while in RCA stenoses the results in the stable group were better (45.1 +/- 17.6% vs 32.7 +/- 12.3%, n.s.). One acute vessel occlusion necessitating an emergency bypass operation occurred in each group (2%). The patient in the stable group died (total mortality rate 1%). Sixty-three of the successfully treated patients were routinely restudied 6 months later. According to clinical symptoms, 23% of the stable and 36% of the unstable group were in functional classes III and IV. From the anatomical viewpoint, a restenosis (greater than 85%) was found in 17% of the stable and in 24% of the unstable group. A further spontaneous decrease (greater than 10%) of the vessel obstruction was found in 47% of the stable group and in 12% of the unstable group.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive assessment of left ventricular performance following transluminal coronary angioplasty

We studied 36 patients with successful transluminal coronary angioplasty (group 1) noninvasively using exercise electrocardiography, exercise T1-201 myocardial scintigraphy and equilibrium radionuclide ventriculography before and 3-5 days after the procedure. Six patients who underwent aortocoronary-bypass surgery (group 2) and 10 patients with stable angina pectoris (group 3) served as controls. All patients had arteriographically documented coronary artery disease at least in one major coronary vessel (stenosis greater than or equal to 70%). In group 1, average coronary stenosis was 81.1 +/- 8.4% before dilatation and 44 +/- 13.7% after the procedure (P less than 0.001). Ischemia score in the exercise electrocardiography decreased from 2.4 +/- 2.7 before dilatation to 0.4 +/- 0.8 after the procedure (P less than 0.001). Myocardial perfusion in computerized T1-201 myocardial scintigraphy 5-10 min after exercise expressed as vitality index (the ratio of T1-201 uptake in the ischemic region to the region of maximal uptake in the same image analyzed carefully in the same view in 2 studies) increased from 72.9 +/- 8.4% before dilatation to 79.9 +/- 11.7% after the procedure (P less than 0.001). Ejection fraction at rest increased from 47.2 +/- 9.2% to 51.0 +/- 9.7% (P less than 0.001) and during exercise from 39.9 +/- 10.5% to 49.4 +/- 10.9% (P less than 0.001) before and after the procedure. In group 2, noninvasive studies showed a tendency to improvement after surgery. In group 3 no significant changes were noted. We conclude that transluminal coronary angioplasty improves both coronary perfusion to ischemic areas supplied by critical coronary artery stenoses and left ventricular function, especially during exercise, if luminal diameter is dilated by greater than 20%.

Rest and redistribution thallium-201 myocardial scintigraphy to predict improvement in left ventricular function after coronary arterial bypass grafting

To examine the value of rest and redistribution thallium-201 imaging in predicting improvement in left ventricular (LV) ejection fraction (EF) after coronary artery bypass grafting (CABG), 26 patients with coronary artery disease (CAD) and abnormal LV function were studied. Nineteen patients had pathologic Q waves preoperatively. Rest and redistribution thallium-201 images and radionuclide ventriculograms were obtained before and after CABG, and the thallium scintigrams were evaluated both quantitatively and qualitatively. The patients were divided according to the preoperative thallium scintigrams into 2 groups: Group I (16 patients) had either normal resting thallium-201 images or reversible resting perfusion defects, and Group II (10 patients) had fixed resting perfusion defects. The resting EF was less than 50% preoperatively in all patients. Fourteen patients (54%) showed improvement in EF postoperatively. Three patients (2 in Group I and 1 in Group II) showed new postoperative perfusion defects, and none of the 3 showed improvement in LV function. Of the remaining 14 patients in Group I, 12 (86%) showed improvement in LV function, compared with 2 of 9 patients in Group II (p less than 0.01). Improvement in LV function was observed in 8 of the 19 patients (42%) with abnormal Q waves. Nitroglycerin intervention radionuclide ventriculograms were obtained in 20 patients before CABG. Of the 6 patients who showed improvement in LV function with nitroglycerin, 4 also showed improvement postoperatively. Postoperative improvement in LV function was also observed in 6 of the 14 patients who did not improve with nitroglycerin. Thus, rest and redistribution thallium imaging is useful in identifying patients whose LV function will improve after CABG. Normal rest thallium-201 images or reversible resting defects correctly identified 12 of 14 patients (86%) who showed improvement in LV function postoperatively. Nitroglycerin-intervention ventriculography and abnormal Q waves were less useful in this differentiation.

Prospective assessment of regional myocardial perfusion before and after coronary revascularization surgery by quantitative thallium-201 scintigraphy

Because thallium-201 uptake relates directly to the amount of viable myocardium and nutrient blood flow, the potential for exercise scintigraphy to predict response to coronary revascularization surgery was investigated in 47 consecutive patients. All patients underwent thallium-201 scintigraphy and coronary angiography at a mean (+/- standard deviation) of 4.3 +/- 3.1 weeks before and 7.5 +/- 1.6 weeks after surgery. Thallium uptake and washout were computer-quantified and each of six segments was defined as normal, showing total or partial redistribution or a persistent defect. Persistent defects were further classified according to the percent reduction in regional thallium activity; PD25-50 denoted a 25 to 50% constant reduction in relative thallium activity and PD greater than 50 denoted a greater than 50% reduction. Of 82 segments with total redistribution before surgery, 76 (93%) showed normal thallium uptake and washout postoperatively, versus only 16 (73%) of 22 with partial redistribution (probability [p] = 0.01). Preoperative ventriculography revealed that 95% of the segments with total redistribution had preserved wall motion, versus only 74% of those with partial redistribution (p = 0.01). Of 42 persistent defects thought to represent myocardial scar before surgery, 19 (45%) demonstrated normal perfusion postoperatively. Of the persistent defects that showed improved thallium perfusion postoperatively, 75% had normal or hypokinetic wall motion before surgery, versus only 14% of those without improvement (p less than 0.001). Whereas 57% of the persistent defects that showed a 25 to 50% decrease in myocardial activity demonstrated normal thallium uptake and washout postoperatively, only 21% of the persistent defects with a decrease in myocardial activity greater than 50% demonstrated improved perfusion after surgery (p = 0.02). Thus, preoperative quantitative thallium-201 scintigraphy appears useful in predicting response to revascularization surgery, and some persistent defects may revert to normal thallium uptake after surgery. Importantly, the preoperative distinction between viable and nonviable myocardium can be reasonably established by quantitating the amount of persistent reduction in thallium uptake and correlating this with preoperative wall motion.

Improvement of resting myocardial asynergy with cessation of upright bicycle exercise

Exercise generally aggravates ischemic myocardial dysfunction, presumably by increasing tissue oxygen demand out of proportion to the increase in supply. Nevertheless, resting left ventricular (LV) wall motion abnormalities can improve dramatically after upright exercise. To investigate this "paradoxical" phenomenon, we performed upright bicycle exercise equilibrium radionuclide ventriculography in 93 patients with angiographic coronary artery disease. Immediately after exercise, LV end-diastolic volume was similar to the resting level (1 +/- 22% of rest value), but end-systolic volume (ESV) was significantly below (p less than 0.05) that at rest (-11 +/- 32%) and LV ejection fraction increased significantly compared with rest (0.57 +/- 0.16 vs 0.51 +/- 0.13, p less than 0.05). Improvement in resting myocardial asynergy was frequent (115 of 330 abnormal segments), and was observed more commonly in patients without pathologic Q waves and in segments manifesting mild rather than severe asynergy. In 60 additional patients with resting asynergy who were also studied after nitroglycerin (NTG), there was 89% concordance of wall motion response in asynergic segments after exercise and NTG: 71 of 85 segments manifesting improvement with NTG also improved after exercise, and 157 of 172 segments without improvement with NTG also failed to improve after exercise. Despite the similar wall motion response, the mechanism of improvement is probably different from that produced by NTG. With NTG, preload (end-diastolic volume) and afterload (systolic blood pressure) were significantly lower than their resting control levels (p less than 0.05). These changes did not occur after exercise. Instead, an isolated, significant reduction in ESV was noted. These data support the hypothesis that catecholamine stimulation is responsible for paradoxical wall motion improvement after upright exercise.

Early assessment of rest and exercise left ventricular function following coronary artery surgery

Radionuclide assessment of rest and exercise left ventricular function was performed in 14 patients before, eight days after, and three months after coronary artery bypass grafting (CABG). Resting function was unaltered after operation, although mild increases in heart rate and end-diastolic volume were observed on the eighth postoperative day. In contrast, exercise function was significantly improved at both postoperative time periods. Exercise ejection fraction was 0.54 +/- 0.10 before operation, 0.73 +/- 0.12 at eight days, and 0.64 +/- 0.13 at three months. Before CABG, the exercise-induced increase in stroke volume was achieved by an increase in end-diastolic volume, whereas eight days after CABG this increase was achieved by an increase in contractility (systolic blood pressure/end-systolic volume). By three months, both contractility and end-diastolic volume increased with exercise. Thus, improvement in left ventricular function during exercise can be documented as early as eight days after coronary revascularization. This change may be less pronounced after three months of convalescence, but considerable improvement in ventricular function persists compared to preoperative assessment.

Serial changes in left ventricular ejection fraction in the early hours after aortocoronary bypass grafting

To determine the course of left ventricular ejection fraction (LVEF) in the early hours after aortocoronary bypass grafting, 24 patients underwent serial gated bloodpool scanning. Twenty-two had received propranolol until the day of surgery. ECGs showed no evidence of perioperative infarction. Preoperatively, the mean (+/- SD) LVEF was 0.56 +/- 0.13; after bypass, it was 0.38 +/- 0.11 at 4 hours, 0.42 +/- 0.12 at 5 hours, 0.43 +/- 0.11 at 6 hours, 0.48 +/- 0.13 at 7 hours, 0.52 +/- 0.15 at 8 hours, and 0.54 +/- 0.15 at 10 to 14 days. The LVEFs at 4, 5, and 6 hours postoperatively were significantly lower than preoperatively (p less than 0.05). Postoperative mean heart rate was higher at all times; mean temperature was depressed at 4 and 5 hours and elevated at 7 and 8 hours; and mean arterial blood pressure was depressed at 7 hours, 8 hours, and 10 to 14 days (p less than 0.05). The degree of the early postoperative LVEF depression correlated with the daily preoperative propranolol dose (p less than 0.05) and was unrelated to bypass time, aortic cross-clamp time, or changes in temperature, heart rate, and blood pressure. The LVEF at 10 to 14 days postoperatively was not significantly different from the preoperative value. The LVEF is depressed in the early hours after aortocoronary bypass grafting and approaches the preoperative value with time. The magnitude of the early depression appears to be related to the preoperative propranolol dose, but does not significantly correlate with factors related to surgical technique.

Preoperative prediction of reversible myocardial asynergy by postexercise radionuclide ventriculography

Myocardial asynergy is sometimes reversed by coronary bypass, and a noninvasive method of predicting which assess are reversible would be desirable. To assess whether changes in myocardial wall motion observed immediately after exercise can differentiate reversible from nonreversible myocardial asynergy, we evaluated 53 patients by radionuclide ventriculography before and after exercise and again at rest after coronary bypass surgery. Preoperative improvement in wall motion immediately after exercise was highly predictive of the surgical outcome (average chance-corrected agreement, 91 per cent). At surgery the asynergic segments that had improved after exercise were free of grossly apparent epicardial scarring. The accuracy of these predictions for postoperative improvement was significantly greater (P less than 0.01) than that of analysis of Q waves on resting electrocardiography (average chance-corrected agreement, 40 per cent). In contrast, preoperative changes in left ventricular ejection fraction after exercise were not predictive of postoperative resting ejection fraction. We conclude that postexercise radionuclide ventriculography can be used to identify reversible resting myocardial asynergy. This test should prove effective in predicting which patients with myocardial asynergy are most likely to benefit from aortocoronary revascularization.

Identification of transient and persistent segmental wall motion abnormalities in patients with unstable angina by two-dimensional echocardiography

To determine the value of real-time, two-dimensional echocardiography (2-D echo) in unstable angina, regional wall motion on serial short-axis 2-D echo recordings was analyzed and summed segment scores of abnormal motion were compared and classified according to each patient's clinical status 12 weeks after hospital discharge. Nineteen male patients who fulfilled criteria for unstable angina and responded to medical therapy underwent 2-D echo study within 48 hours of admission and discharge. Of 11 patients with abnormal 2-D echo scores on admission, five patients had reduced scores and six patients had similar or increased scores at discharge. Six of eight patients who had scores of zero on admission had scores of zero at discharge. At follow-up, 11 patients had minimal or no angina pectoris (group 1), and eight patients had worsening angina or recurrent unstable angina (group 2). At discharge, 2-D echo studies showed that all group 1 patients had reduced or zero scores, while group 2 patients retained or increased their abnormal scores. This study shows that in patients with unstable angina, both transient and persistent abnormalities can be identified by 2-D echo. Abnormal segmental wall motion was transient or absent in patients with a good outcome, and worsened or remained abnormal in patients with a poor outcome.

Characteristic electrocardiographic pattern indicating a critical stenosis high in left anterior descending coronary artery in patients admitted because of impending myocardial infarction

In patients admitted to the hospital because of unstable angina, a subgroup can be recognized that is at high risk for the development of an extensive anterior wall myocardial infarction. These patients, who show characteristic ST-T segment changes in the precordial leads on or shortly after admission, have a critical stenosis high in the left anterior descending coronary artery. Of 145 patients consecutively admitted because of unstable angina, 26 (18%) showing this ECG pattern, suggesting that this finding is not rare. In spite of symptom control by nitroglycerin and beta blockade, 12 of 16 patients (75%) who were not operated on developed a usually extensive anterior wall infarction within a few weeks after admission. In view of these observations, urgent coronary angiography and, when possible, coronary revascularization should be done in patients with unstable angina who show this ECG pattern.

Use of thallium-201 redistribution scintigraphy in the preoperative differentiation of reversible and nonreversible myocardial asynergy

Thallium-201 (201Tl) redistribution scintigraphy might differentiate reversibly from nonreversibly asynergic myocardial segments and thus predict the response of these segments to coronary artery bypass grafting (CABG). To test this hypothesis, 25 consecutive patients undergoing CABG, preoperative stress-redistribution 201Tl scintigraphy, and both pre- and postoperative resting equilibrium radionuclide ventriculography were evaluated. For both types of scintigraphic study, each patient was imaged in the same three views. Because of the effects of CABG on septal motion, this region was considered separately. Postoperative improvement was noted in 54% of 72 preoperative asynergic segments. Improvement was common not only in hypokinetic but also in akinetic and dyskinetic segments, and occurred in a similar proportion of studies performed early (less than 2 weeks) or late (3-6 months) after CABG. Thallium-201 redistribution scintigraphy was highly predictive of the pattern of postoperative asynergy: The redistribution pattern was normal in 90% of segments with reversible asynergy and abnormal in 76% of segments with nonreversible asynergy. The presence or absence of pathologic Q waves was less sensitive in this differentiation. Septal segments, however, frequently demonstrated abnormal wall motion postoperatively, despite normal 201Tl redistribution scintigraphy. Resting left ventricular ejection fraction (LVEF) was generally unchanged postoperatively, but in some patients with multiple areas of reversible asynergy it did improve. Thus, 201Tl redistribution scintigraphy appears to reliably distinguish viable from nonviable asynergic myocardial zones, and predicts the response of these segments to CABG.

Exercise thallium 201 scintigraphy in evaluating aortocoronary bypass surgery

Thirty patients with recurrent symptoms after aortocoronary bypass graft surgery underwent angiography as well as exercise thallium 201 imaging. Exercise imaging has been shown to be highly specific (100 percent in our study) in evaluating patients after bypass surgery. Patients with complete revascularization have normal thallium 201 images. Similarly, exercise-induced defects are seen only in the presence of incomplete revascularization. There are patients, however, with incomplete revascularization with normal exercise images, but these generally limited to the right coronary artery or the diagonal vessels or their grafts.

Use of exercise tests in assessment of the functional result of aortocoronary bypass surgery

The value of an objective exercise test for the assessment of the functional results of aortocoronary bypass was investigated in 19 patients who were studied before and six months after the operation. For positive tests the end point was defined as a net ST segment depression of 0·1 mv 80 ms after the J point of the ECG. For negative tests the end point was 85% of the age-predicted maximal heart rate response. One patient who was not able to attain either of these points after the operation was excluded. In the remaining 18 patients three indices were used in the analysis. First, the heart rate (HR) and the product of heart rate and systolic blood pressure (RPP) were measured at the defined level of ST segment depression during positive exercise tests to yield HR/ST and RPP/ST threshold respectively. Second, the HR and RPP were measured at the end point of the negative tests. Third, the duration of exercise till the end point of the tests was measured. In each patient the duration of the postoperative test was longer than that of the preoperative test. While all the patients had a positive exercise test before the operation, the test was negative in 11 after it. In 10 of these 11 patients the HR and RPP attained at the end point of the postoperative test had increased; the HR and RPP remained unchanged in one patient. Positive tests were still present in seven of the 18 patients. In five of these the HR/ST threshold and RPP/ST threshold were greater after than before operation, and they remained unchanged in two. An improvement in myocardial blood supply after aortocoronary bypass was suggested indirectly by the ability to attain, during exercise, a higher HR and RPP at the end point of the test. The test proved especially valuable in patients who retained a positive exercise test after the operation.

Relationship of thallium-201 myocardial perfusion pattern to regional and global left ventricular function with exercise

Thallium-201 redistribution pattern after exercise was related to rest and exercise left ventricular regional and global function, measured by radionuclide ventriculography, in 61 patients, 50 with coronary artery disease (CAD). Sixteen patients had exclusively transient thallium defects, suggesting ischemia: in this group, mean left ventricular ejection fraction (LVEF) was 65% at rest, falling to 58% during exercise (p less than 0.01). Eight patients had exclusively persistent thallium defects, suggesting scar: LVEF was unchanged during exercise, 58% to 59%. LVEF increased during exercise in the 17 patients without exercise thallium defects, seven with CAD: 66% to 73% (p less than 0.05). Individual LV wall segments which exhibited transient or persistent thallium defects contracted abnormally both at rest and during exercise; (2) both transient and persistent thallium defects can be associated with resting dyssynergy; and (3) in some CAD patients, apparent hypoperfusion does not necessarily predict left ventricular dysfunction during exercise.

Aortocoronary bypass grafting in patients without left main stenosis. Relation of risk factors to early and late survival

Three-hundred and thirty-five patients without left main stenosis or recent acute myocardial infarction underwent isolated aortocoronary bypass grafting during 1974 and 1975. The hospital mortality was 2 per cent for the four-year predicted survival is 94 per cent. Neither the preoperative presence or absence of a progressive or unstable angina pattern, the extent of coronary artery disease, nor the left ventricular ejection fraction predicted postoperative survival. None of the 25 patients whose ejection fraction was 0.30 or less died in the perioperative period, and no late deaths occurred in this subgroup until after 36 months of follow-up, giving a predicted four-year survival rate of 82 per cent. With only one exception, patients in this subgroup were operated on because of angina, which was unstable in three-quarters of them. We believe that this study shows that patients with a severely reduced ejection fraction should not be refused aortocoronary bypass grafting if symptoms of angina are severe and predominate over symptoms of heart failure.

Pharmacologic intervention in cardiovascular nuclear medicine procedures

Relevant questions in ischemic heart disease are (1) what is the ischemic threat? (2) What is the extent of ventricular dysfunction? (3) Is the observed dysfunction reversible? Exercise testing can help to identify the ischemic threat. Catheterization studies have shown that resting ventricular dysfunction can be reversed in some patients through pharmacologic or surgical intervention. However, improved ventricular performance in ischemic heart disease may be achieved through a variety of mechanisms. Insight into all components of cardiac performance (regional and global contractillity, preload, afterload, and heart rate) and myocardial perfusion may be required to adequately describe the influence of intervention. Exercise radionuclide ventriculographic studies have demonstrated that stress-induced ventricular dysfunction can be reversed through surgical and pharmacologic intervention. Studies at rest have demonstrated that radionuclide techniques can detect drug-induced changes in ventricular performance in groups of patients. The challenge to cardiovascular nuclear medicine is the prospective identification of patients who would benefit most from aggressive intervention aimed at preventing or reversing ischemic ventricular dysfunction.

Influence of potassium cardioplegia versus ischemic arrest on regional left ventricular diastolic compliance in humans

To compare the effects of hypothermic ischemic arrest versus hypothermic potassium cardioplegia, regional left ventricular performance was monitored in 20 adult male patients undergoing saphenous vein bypass operation. Twelve patients received ischemic arrest (Group 1), and 8 received potassium cardioplegia (Group 2). Groups 1 and 2 did not differ in left ventricular ejection fraction (0.62 versus 0.60), number of bypassed vessels (3.7 versus 3.4), mean cross-clamp time (75 versus 63 minutes), or mean cardiopulmonary bypass time (182 versus 170 minutes). Before cardiopulmonary bypass was begun, a pair of ultrasonic crystals was secured in the left ventricular anterior myocardium to measure segment motion and a micromanometer-tipped catheter was placed in the left ventricular chamber. All patients received a saphenous vein bypass graft to a vessel supplying the anterior left ventricular wall in the region of the ultrasonic crystals. Comparison of changes in systolic measurements revealed no significant differences between Groups 1 and 2. After saphenous vein bypass grafting, the left ventricular end-diastolic pressure (11.4 to 17.0 mm HG) and modulus of left ventricular segment stiffness (0.37 to 0.67, p less than 0.02) were elevated in Group 1 but no changes were observed in Group 2 (14.0 to 15.6 mm Hg, and 0.16 to 0.24, respectively). Compared with hypothermic ischemic arrest, hypothermic potassium cardioplegia is not associated with an increased left ventricular diastolic stiffness shortly after saphenous vein bypass grafting in humans.

Treatment of unstable angina pectoris with percutaneous transluminal coronary angioplasty (PTCA)

Percutaneous transluminal coronary angioplasty (PTCA) was performed in 40 patients (34 male, 6 female; 51.0 +/- 8.5 years) with the typical clinical picture of unstable angina. All had a short history of pain (2.9 +/- 2.0 months), angina at rest, transient ST and/or T wave changes during this period, and little or no enzyme elevations. The patients had a total of 41 stenoses (39 single, one double; one main-stem, 26 left anterior descending, 14 right coronary artery). The degree of the stenoses was 95.5 +/- 4.9% (area method) and 81.8 +/- 10.7% (diameter method). PTCA was successfully performed in 26 cases (63%), reducing the stenoses to 61.5 +/- 12.4% (area method) and 39.1 +/- 10.0% (diameter method). One patient (2.5%) received an immediate bypass operation because of an acute vessel occlusion. Eleven of the 14 not successfully treated patients received an aortocoronary bypass within the next three to 35 days. All still had symptoms of unstable angina. Three patients refused operation. Their treatment consisted of nitroglycerin, beta-blockers and nifedipin. Seventeen of the 26 successfully treated patients were restudied after 4.9 +/- 1.7 months. The degree of stenosis had risen to 69.2 +/- 17.4% (area method). While the stenoses in 12 patients were equal or less than before PTCA, stenosis recurred in five cases. Two patients were successfully retreated. PTCA can be performed with a good early success rate and a low concentration rate in patients with unstable angina. Relief of pain and improvement of blood supply to the jeopardized myocardium can be provided immediately and with a limited amount of expense. The method can therefore be regarded first-stage treatment in such patients.

Patency and flow response in endarterectomized coronary arteries

Ninety patients, operated on from May, 1978, through June, 1979, underwent coronary endarterectomy and early recatheterization. Patency of grafts to endarterectomized arteries was 103 of 118 (87.3%) and patency of conventional vein grafts in the same patients was 217 of 233 (93.1%). Myocardial blood flow using xenon 133 washout, at rest and with isoproterenol-induced stress, was measured in 7 normal coronary arteries, 28 conventional saphenous vein grafts, and 33 saphenous vein grafts to endarterectomized coronary arteries. The increase in myocardial blood flow, from rest to isoproterenol-induced stress, was comparable for the three groups. The endarterectomized group was divided further by separating out the 10 patients with heavy scarring or residual disease. The remaining patients had a flow response identical to those with conventional saphenous vein grafts. The rate of perioperative infarction in patients receiving endarterectomy was 3 of 113 (2.6%), as measured by appearance of new persistent Q waves on the serial postoperative electrocardiogram. Positive pyrophosphate scans were noted in 12 of 105 (12.4%) patients. It is concluded that, in the early stages at least, grafts to endarterectomized coronary arteries stay open and perfuse the myocardium as well as conventional saphenous vein grafts unless the myocardium is heavily scarred or unless residual disease remains.