Kazuto Yamanishi

Significance of preinfarction angina for preservation of left ventricular function in acute myocardial infarction.

The effect of preinfarction angina on the preservation of left ventricular function was evaluated with the use of cineventriculography in 37 patients who had either total or subtotal occlusion of the proximal left anterior descending coronary artery during the convalescent period of myocardial infarction. In 15 patients who had preinfarction angina more than 1 week before the onset of acute myocardial infarction (group A), the global left ventricular ejection fraction was 54 +/- 3% (SEM) and regional wall motion in the infarct area was 10 +/- 3%. In 10 patients who had preinfarction angina occurred within 1 week before the onset of acute myocardial infarction (group B), the left ventricular ejection fraction and regional wall motion in the infarct area were 42 +/- 3% and 1 +/- 2%, respectively. In 12 patients without preinfarction angina (group C), the left ventricular ejection fraction and regional wall motion in the infarct area were 38 +/- 3% and -1 +/- 2%, respectively. In groups B and C, both the left ventricular ejection fraction and regional wall motion in the infarct area were lower than those in group A (p less than 0.05). The collateral circulation at the onset of acute myocardial infarction was better in group A compared with groups B and C (p less than 0.05). Thus the collateral circulation, promoted by repetitive anginal episodes indicative of myocardial ischemia, causes the preservation of myocardial function.

Importance of ischemic preconditioning and collateral circulation for left ventricular functional recovery in patients with successful intracoronary thrombolysis for acute myocardial infarction

We studied the effects of myocardial ischemic preconditioning and preexistent collateral circulation on the preservation of left ventricular function in 30 patients who had successful intracoronary thrombolysis within 6 hours after the onset of a first acute anterior myocardial infarction. The existence of ischemic preconditioning was defined as the episode of recurrent ischemic chest pain within 4 hours before the onset of acute myocardial infarction. In 16 patients with ischemic preconditioning (group A), the left ventricular ejection fraction during the convalescence of myocardial infarction was 57% +/- 11% (mean +/- SD); regional wall motion in the infarct area was 13% +/- 9%. In 14 patients without ischemic preconditioning (group B), the left ventricular ejection fraction and regional wall motion in the infarct area were 46% +/- 9% and 5% +/- 9% (both p < 0.05 vs group A). Moreover, among group A patients, seven patients having a well-developed collateral circulation during the acute stage of myocardial infarction showed a more prominent improvement in regional wall motion in the infarct area compared with nine patients having poor or no collateral circulation (18% +/- 8% vs 9% +/- 7%, p < 0.05). These data indicate that ischemic preconditioning is effective for the preservation of left ventricular function in patients with successful intracoronary thrombolysis and that preexistent coronary collateral circulation potentiates this favorable effect of ischemic preconditioning.

Importance of coronary collateral circulation for kinetics of serum creatine kinase in acute myocardial infarction

The effect of coronary collateral perfusion on the kinetics of creatine kinase (CK) was examined in 32 patients undergoing intracoronary thrombolysis within 6 hours after the onset of a first acute myocardial infarction (AMI). Blood sampling for CK was performed every 2 to 4 hours for a period of 72 hours after AMI. The cumulative CK release was determined using the integrated appearance function curve with the individual disappearance rate. In 19 patients in whom thrombolysis was successful (group A), time to peak CK level was 11 +/- 1 (standard error of the mean) hours after AMI and cumulative CK release was 2,599 +/- 424 U/liter. In 6 patients who had a significant collateral circulation to the infarct-related coronary artery and unsuccessful reperfusion (group B), the time to peak CK was 16 +/- 1 hours (p less than 0.05 compared with group A) and cumulative CK release was 1,897 +/- 478 U/liter (difference not significant compared with group A). In the remaining 7 patients, with neither recanalization nor significant collateral perfusion group C, time to peak CK was 21 +/- 1 hours and significantly (p less than 0.05) longer than groups A and B. Cumulative CK release (2,707 +/- 776 U/liter) was not significantly different from groups A and B. Thus, collateral perfusion is an important determinant of the CK time-activity curve during AMI. Early peaking of CK levels does not reliably identify spontaneous or drug-induced recanalization of the infarct-related coronary artery.

Circadian variation in the success rate of intracoronary thrombolysis for acute myocardial infarction

Abstract Intracoronary thrombolytic therapy for acute myocardial infarction (AMI) has been demonstrated to be effective in terms of the limitation of myocardial necrosis, the preservation of left ventricular function and the improvement of survival. 1–3 The recanalization rate by intracoronary thrombolysis has been reported to be affected by various factors, such as the type and dose of thrombolytic agents, 4,5 and the extent of underlying stenosis severity of the infarct-related coronary artery. 6,7 It is postulated that the recanalization rate is influenced by the level of plasminogen activator inhibitor which is one of the major components of the fibrinolytic system. In the present study we measured a circadian variation in the success rate of intracoronary thrombolysis, as there is a report that plasminogen activator inhibitor activity is markedly increased during the early morning hours. 8

Significance of collateral circulation in reversible left ventricular asynergy by nitroglycerin in patients with relatively recent myocardial infarction

To evaluate the functional role of coronary collateral circulation in reversible asynergy of the left ventricle, cineventriculography was performed before and after the administration of sublingual nitroglycerin in 19 patients with complete occlusion of the proximal part of the left anterior descending coronary artery. In nine patients who had significant collateral circulation to the infarct-related coronary artery (group A), there was significant improvement in both the left ventricular ejection fraction (53% to 60%, p less than 0.05) and regional wall motion in the infarct zone (8% to 18%, p less than 0.01 in the anterolateral area) with administration of nitroglycerin. In contrast, in the remaining 10 patients without significant collateral perfusion (group B), there were no detectable changes in either global function (49% versus 50%) or regional wall motion (6% versus 8% in the anterolateral area) before and after nitroglycerin. Changes in heart rate and left ventricular peak systolic and end-diastolic pressures with nitroglycerin were comparable in both groups. These results suggest that angiographically demonstrable collaterals preserve viable myocardium, which can improve its contraction when the supply-demand relationship is favorably affected because of increased collateral flow and/or more favorable loading conditions produced by nitroglycerin.

Comparative effect of heparin treatment with and without strenuous exercise on treadmill capacity in patients with stable effort angina

It has recently been demonstrated that treadmill capacity and collateral circulation improve as a result of exercise with heparin pretreatment in patients with effort angina. In the present study, we assessed whether heparin alone is effective in increasing treadmill capacity in 14 patients with effort angina. Patients were randomly assigned to one of two treatment arms: (1) group A--20 treadmill exercise periods with standard Bruce protocol twice a day for 10 days with heparin (5000 IU intravenously) pretreatment (seven patients) or (2) group B--10 injections of heparin calcium (10,000 IU subcutaneously) once a day for 10 days (seven patients). In group A, total exercise time was increased from 6.9 +/- 1.2 (SD) to 9.9 +/- 1.9 minutes (p less than 0.0005), as was the maximal double product, from 21,700 +/- 3,500 to 27,000 +/- 4,800 mm Hg/min (p less than 0.05). The double product at the onset of angina was also increased by 34% (p less than 0.05), and the double product at which ST depression (0.1 mV) first appeared was 22% (p less than 0.05) greater after treatment. In contrast, in group B, all of the above-mentioned parameters of treadmill capacity remained unchanged. These data indicate that heparin does not serve as an angiogenic factor by itself, but that it potentiates the ischemia-derived angiogenic factor.

Effects of heparin treatment on collateral development and regional myocardial function in acute myocardial infarction

To define the effects of heparin treatment during the acute stage of the first anterior myocardial infarction on coronary collateral development and regional myocardial function, we evaluated angiographically the extent of a collateral visualization (collateral index: 0-3) to the completely obstructed infarct-related coronary artery and regional wall motion in 18 patients during convalescence after infarction. The patients were divided into two groups depending on the presence (group I) or absence (group II) of heparin treatment (170 to 220 IU/kg per day) during the acute phase of infarction. The collateral index was significantly higher in group I (1.5 +/- 0.9) than in group II (0.4 +/- 0.4; p less than 0.05). The left ventricular ejection fraction tended to be greater in group I than in group II (49 +/- 12% vs 38 +/- 16%), and there was a significant difference in regional wall motion of the infarct area that was evaluated by the percentage of segment shortening between the two groups (group I:7.4 +/- 9.2%, group II:-0.8 +/- 4.5%, p less than 0.05). These findings indicate that heparin treatment for patients with acute myocardial infarction is worthwhile in terms of the preservation of left ventricular function as a result collateral development.

Collateral circulation as a marker of the presence of viable myocardium in patients with recent myocardial infarction

The relationship between the presence of viable myocardium and the extent of coronary collateral circulation to the infarct area was evaluated in 20 patients with a recent anterior myocardial infarction who had complete obstruction of the left anterior descending coronary artery. The viability of myocardial tissue was assessed by exercise thallium-201 myocardial scintigraphy, and the collateral circulation was angiographically evaluated by means of a collateral index ranging from 0 to 3. Patients were divided into two groups according to the presence (group 1, n = 10) or absence (group 2, n = 10) of viable myocardium in the perfusion territory of the infarct-related artery. The collateral index in group 1 was 2.5 +/- 0.5 (SD), which was significantly higher than the 0.7 +/- 0.8 in group 2. These findings indicate that the presence of ischemic but viable myocardium is intimately related to the development of collateral circulation in patients with myocardial infarction, and the existence of well-developed collateral channels predicts the presence of viable myocardium in the infarct area.

Preferential dilation of recipient coronary arteries of the collateral circulation by intracoronary administration of nitroglycerin

OBJECTIVES The purpose of this study was to test the hypothesis that the sensitivity to nitroglycerin of collateral vessels and recipient arteries is greater than that of donor arteries of the collateral circulation. BACKGROUND The collateral circulation responds vigorously to nitroglycerin. However, the mechanisms of the efficacy of nitroglycerin for improving collateral circulation are not fully elucidated. METHODS The diameter of donor and recipient arteries of the collateral circulation was measured with a computer-assisted analysis system in eight patients with well developed collateral vessels. Coronary angiography was repeated before and after the intracoronary injection of 50 micrograms of nitroglycerin. RESULTS After nitroglycerin, the mean diameter +/- SD of donor arteries increased to 1.61 +/- 0.53 from 1.29 +/- 0.39 mm (p < 0.01), whereas the diameter of recipient arteries increased to 1.59 +/- 0.50 from 1.10 +/- 0.49 mm (p < 0.01). The change in the diameter of recipient arteries was significantly greater than that of donor arteries (52.3 +/- 24.6% vs. 24.7 +/- 11.5%, p < 0.05). These changes induced by the intracoronary injection of nitroglycerin were accompanied by a decrease in pacing-induced ST segment depression (0.16 +/- 0.06 to 0.06 +/- 0.04 mV, p < 0.01), suggesting increased flow reserve through collateral channels. CONCLUSIONS These findings indicate that the sensitivity to nitroglycerin of recipient arteries of the collateral circulation is significantly greater than that of donor arteries. This observation may explain the strong response of the collateral circulation to nitroglycerin in patients with functionally significant collateral channels.

Relation between collateral channel filling and flow grade in recipient coronary arteries in patients with stable effort angina

OBJECTIVES The purpose of the present study was to elucidate the relation between the extent of perfusion of the ischemia-related coronary artery and the degree of visualization of the collateral circulation to the ischemic area. BACKGROUND Because it is difficult to accurately assess coronary stenosis severity with standard angiographic techniques, the inclusion of flow grade in recipient coronary arteries would provide an additional perspective concerning the effect of the progression of atherosclerotic obstructive disease on the development of collateral circulation. METHODS The coronary arteriograms of 54 consecutive patients with chronic effort angina without prior myocardial infarction were examined. Patients were classified into four groups according to the extent of perfusion of the ischemia-related coronary artery (Thrombolysis in Myocardial Infarction [TIMI] grade 0 to 3). The degree of angiographically demonstrable collateral circulation was also classified into four grades (collateral index 0 to 3). RESULTS Eighteen patients had TIMI grade 0, 6 had grade 1, 13 had grade 2 and 17 had grade 3 perfusion. The collateral indexes of TIMI 0, 1, 2 and 3 groups were 2.7 +/- 0.7 (mean +/- SEM), 2.2 +/- 0.6, 1.2 +/- 1.1 and 0.4 +/- 0.9, respectively (p < 0.01 vs. TIMI 0, p < 0.05 vs. TIMI 1). CONCLUSIONS These findings indicate that all patients with chronic effort angina have the potential for collateral development as a result of coronary artery narrowing, and the functional state of well developed collateral vessels may be primarily determined by the pressure gradient across the collateral network.