Regional myocardial shortening in relation to graft-reactive hyperemia and flow after coronary bypass surgery

Effect of flecainide on regional left ventricular wall motion after acute intravenous, acute oral and chronic oral administration late after coronary artery bypass grafting

Epicardial marker motion was measured in 14 patients before flecainide administration, immediately after an intravenous dose of 2 mg/kg over 15 minutes (maximum 150 mg) and 15 minutes thereafter. Platinum epicardial markers had been implanted more than 4 years earlier at the time of coronary artery bypass grafting. Maximal and minimal marker separation (Lmax and Lmin) during the cardiac cycle were measured and regional shortening fraction (Lmax - Lmin)/Lmax) was determined as a percentage. After intravenous flecainide, a significant increase in end-diastolic (immediately after 2.8%; after 15 minutes 2.1%) and end-systolic (3.6% and 3.2%) regional dimensions was observed, together with a decrease in regional myocardial shortening (9.3% and 9.0%). One week later, after a single oral dose of 200 mg of flecainide, Lmax and Lmin had increased 2.4% and 2.7%, while regional myocardial shortening did not differ significantly from baseline values. In 10 patients measurements were repeated after 6 weeks of chronic oral treatment with 300 mg/day. Despite plasma flecainide levels similar to those after intravenous administration, no significant changes in end-diastolic and end-systolic dimensions or regional shortening fraction were observed. Thus, acute intravenous or oral flecainide administration increases regional end-diastolic and end-systolic dimensions, but only intravenous administration decreases regional shortening fraction. Values during chronic administration indicate that regional myocardial function is more affected at the time of rising or acutely changing flecainide plasma levels than when stable plasma levels are achieved.

Improved graft patency in patients treated with platelet-inhibiting therapy after coronary bypass surgery

One hundred forty-seven consecutive coronary bypass patients were enrolled in a randomized, double-blind, risk-stratified, placebo-controlled prospective trial evaluating the effect on graft patency of 325 mg tid aspirin (ASA) plus 75 mg tid dipyridamole (DP) or ASA alone. One hundred twenty-seven patients (399 total grafts) underwent surgery, initiation of drug therapy 67 +/- 27 (SD) hr postoperatively, five clinic visits, and repeat angiography at 1 year. A logistic regression statistical model was used to determine the effects of 28 different measured variables on graft patency and to adjust for these effects in determining the relationship between antiplatelet therapy and graft occlusion. No patient-specific variable contributed significantly to the prediction of occlusion in either the placebo or the treated group. Six graft-specific variables (arterial diameter, severity of stenosis, graft flow, reactive hyperemia, presence or absence of collaterals, and graft type) did contribute and were included in the model. Twenty-one percent of placebo-treated grafts became occluded. Compared with placebo, the relative risk of graft occlusion with ASA was 0.47 (p = .04); with ASA + DP, it was 0.50 (p = .04). This benefit was principally due to reduction of occlusion in the most common and presumably most important groups of grafts, those in which flow exceeded 40 ml/min, or supplying arteries having luminal diameters greater than 1.5 mm. Grafts lacking reactive hyperemia had a 32% occlusion frequency in placebo-treated patients; relative risk of their occlusion averaged 0.26 (p less than .01) with platelet-inhibiting therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular wall motion: its dynamic transmural characteristics

Cardiac wall motion has been studied extensively. It is usually determined by indirect two-dimensional measurements for the true three-dimensional (3D) motion with its specific speed and direction. Errors are also introduced by using internally fixed reference systems and by the inability to identify precise points on the heart wall during the cardiac cycle. Because of these limitations, the endocardial and epicardial wall motion and their relationship are still unclear. This study was designed to assess endocardial and epicardial wall motion by measuring the direction and speed of implanted markers in an externally fixed 3D coordinate system. Fifty-seven pairs of endocardial and epicardial metallic markers were placed at anterior, lateral, posterior, basal, and apical regions of the left ventricles of 14 normal mongrel dogs. Biplane cineradiographs were performed at 50 frames/sec, and the 3D motions of the markers were analyzed using a specially designed computer system. It was found that the speeds, directions, displacements, and phases of the movements of corresponding endocardial and epicardial points were highly correlated. The correlation coefficients were 0.77 to 0.95 for the mean directions, 0.61 to 0.96 for the mean speeds, and 0.59 to 0.96 for the mean displacements at various regions of the heart, and the periodic movements of the endocardium and epicardium were always in phase. The mean epicardial speeds and displacements are fixed proportions (approximately 70%) of the mean endocardial speeds and displacements despite the differences in absolute values between regions in the same dog and the same regions in different dogs. The correlation coefficients for endocardial and epicardial instantaneous speeds, directions, and velocities ranged from 0.68 to 0.83, 0.81 to 0.88, and 0.77 to 0.86, respectively, for different regions of the heart. The correlation coefficients were significant for both the mean values and the instantaneous values. Thus, when only fixed epicardial points are accessible for wall motion measurements in clinical situations, it is possible to infer the endocardial motion from the epicardial motion.

Non-invasive Assessment of Regional Myocardial Function at Rest and during Exercise after Aorto-coronary Bypass Operation

Fifty patients (mean age 53.9 years) with persistent severe ang na pectoris underwent aorto-coronary bypass surgery receiving an overall of 161 anastomosis. On an average 8.6 ± 1.3 months p.o. first pass radionuclide ventriculograms with 99 m Technetium-Pertechnetate were performed at rest and after maximum exercise. Regional ejection fractions (REF) was assessed defining REF as motion of a left ventricular piece of myocardium which is supplied by one main coronary artery and its branches.

All regions were classified using preoperative coronary angiograms and operative reports. Six groups evolved:

Group 1: (normally perfused areas; n = 14): Total group's REF increased after exercise by 11.6 percentage points.

Group 2 (completely revascularized regions without previous myocardial infarction (M.I.); (n=55): On an average REF improved by 11.0 points.

Group 3 (completely revascularized regions with previous M.I.; n=25): After exercise REF still rose by 4.1 percentage points. The results deteriorated further in the remaining three groups:

Group 4 (incompletely revascularized territories without previous M.I.; n=19), decrease of REF by —4.9 points,

Group 5 (incompletely revascularized territories with previous M.I.; n=8) deterioration by —8.1 points.

Group 6 (no revascularization but significant disease with or without previous M.I.; n=14) did not differ from group 5; REF deteriorated by —9.0 percentage points.

The findings show that complete revascularization improves REF significantly (p < 0.05). Areas without previous M.I. respond to exercise like normally perfused territories.

Angina pain relief subsequently to aorto-coronary bypass surgery is undisputed. Yet, up till now, improvement of left ventricular function seemed questionable. One reason for the ineptitude might be the global access to left ventricular function. Since coronary artery disease has segmental nature, global left ventricular parameters, like global ejection fraction e.g., may hide regional changes achieved by revascularization. Therefore, evidence of functional improvement should be done regionally. In the presented study regional ejection fraction was applied, defining that term as motion of a left ventricular portion, which is supplied by one main coronary artery and its branches.

Regional left ventricular function in the three main coronary artery territories at rest and during exercise

Twenty consecutive patients (mean age 51.6 years) with persistent severe angina pectoris underwent aorto-coronary bypass surgery receiving an overall of 60 anastomosis. On an average, 9.4 +/- 1.5 months p.o. first pass radionuclide ventriculograms (18 to 24 mCi 99m Technetium-Pertechnetate i.v.) were performed at rest and after exercise. Besides measurement of global ejection fraction (GEF), regional ejection fraction (REF) was assessed employing for the first time a new technique: each RAO-view of p.o. radionuclide left ventriculogram was subdivided into three regions according to supply of the three main coronary arteries and their branches as visualized on pre-operative coronary angiogram. GEF improved after maximum exercise in 13 cases by 8.1% points (from 50.4 to 58.5%), remained unchanged three times and decreased four times by 7.1 points (from 51.6 to 44.5%; all changes p less than 0.05). In completely revascularized regions (n = 35) REF improved 24 times by 9.7 points (from 51.1 to 60.8%), did not differ from rest REF six times and decreased in three case by 7.3 points (from 48.6 to 41.3%; all changes p less than 0.05). completely revascularized regions responded to exercise like normally perfused areas (increase 7.8 points (from 50.6 to 58.4%; n = 7; p less than 0.05). REF deteriorated in incompletely revascularized regions (n = 9) six times by 12.8 points (from 58.0 to 45.2%), remained unchanged twice and improved once by 4.5 points. Total group's REF decreased by 7.3 points (from 56.8 to 49.5%; p less than 0.05). Exercise REF of incompletely revascularized regions was highly significant inferior to that of completely revascularized regions (49.5 to 58.4%; p less than 0.01). GEF is a weighted balanced of the three regional ejection fractions. The most important parameter is REF of LAD territory.