Role of transient ischaemia and perioperative myocardial infarction in the genesis of new septal wall motion abnormalities after coronary bypass surgery

Is off-pump coronary artery bypass surgery superior to on-pump coronary artery bypass surgery on postoperative paradoxical ventricular septal motion?

BACKGROUND

The aims of this study were to investigate the appearance of paradoxical ventricular septal motion (PSM) after coronary artery bypass graft (CABG) surgery and to identify factors that might be related to this abnormality.

METHODS

This prospective study included 119 consecutive patients (38 women, 81 men) who underwent CABG. Patients who underwent on-pump surgery (22 women, 45 men) and patients who underwent off-pump surgery (16 women, 36 men) were studied separately. All subjects underwent preoperative angiographic septal perfusion evaluation, pre- and postoperative echocardiography, and standard electrocardiographic and laboratory investigations, including troponin I and CK-MB levels. Multivariate logistic regression analysis was also performed for a variety of related parameters.

RESULTS

Significant differences in EuroSCORE, length of intensive care unit stay, length of hospital stay, PSM (assessed using echocardiography), septal perfusion (observed using preoperative angiography), postoperative pleural effusion, and intensive care unit recidivism were observed between the two groups (P < .05). Moreover, postoperative PSM was correlated with septal perfusion (r = -0.687**, P < .001), type of operation (r = -0.194*, P = .035), diabetes mellitus (r = 0.273**, P = .003), carotid stenosis (r = 0.235*, P = .011), the number of distal anastomoses (r = 0.245**, P = .008), pleural effusion (r = 0.193*, P = .037), and intensive care unit recidivism (r = 0.249**, P = .007). However, multivariate analysis demonstrated that only preoperative septal perfusion (odds ratio: 0.037; 95% confidence interval: 0.011-0.128; P < .05) constitutes an independent risk factor for PSM (P < .05).

CONCLUSIONS

This study demonstrated that preoperative septal perfusion deficiency represents an independent risk factor for postoperative PSM in patients undergoing CABG. Further investigations addressing the timing of the appearance of PSM and the correlation of this finding with perfusion imaging studies may provide new details concerning the mechanisms that underlie this abnormality.

Correlation of akinesia with graft patency and cardiac enzyme after off-pump coronary artery bypass graft surgery

BACKGROUND

The aim of the present study was to identify the clinical implications of newly developed akinesia in echocardiography after off-pump coronary artery bypass graft (CABG) surgery and its relationship with graft patency.

METHODS AND RESULTS

A total of 512 patients underwent off-pump CABG from January 2007 to November 2008. Two hundred and thirty-nine patients, whose echocardiography and multi-slice computed tomography data were available, were included in the study. Wall motion was subdivided into 16 segments and analyzed. Patients were separated into group A with newly developed akinesia (n=20), and group B without newly developed akinesia (n=219). Morbidity and early mortality, cardiac enzyme level, and graft patency were compared. The incidence of newly developed akinesia according to the anatomical territory was as follows: anterior, 5; lateral, 3; posterior, 7; and multiple territories, 5. Significant differences in preoperative ejection fraction were observed between the 2 groups (group A, 45.0+/-7%; group B, 58.0+/-12.2%, P<0.001). There was no statistical difference in the mean number of bypassed grafts and the complete revascularization rate. Complication and early mortality rates were insignificant between the 2 groups. There was little association between graft patency, cardiac enzyme level, and newly developed akinesia (P>0.05). Multivariate analysis showed that the preoperative ejection fraction was a risk factor for newly developed akinesia.

CONCLUSIONS

The mechanism of development of akinesia after off-pump CABG might be attributable to intraoperative coronary malperfusion, which is probably due to cardiac manipulation rather than graft occlusion.

Heterogeneous distribution of cardioplegic solution in pigs

Septal dyskinesia in the left ventricle is detected frequently in many patients after open-heart surgery. The present study was designed to determine whether the antegrade delivery of cardioplegic solution to the regional wall categorized in echocardiography is homogeneous, and whether the distribution to the septal wall differs from that to the lateral wall in the absence of coronary artery disease. To assess these hypotheses quantitatively, radioactive microspheres were mixed into the cardioplegic solution and infused by an antegrade method in eight normal pigs. The cardioplegic distribution to the septal wall was significantly less than to the lateral wall close to the base of the left ventricle (P<0.05). Therefore, antegrade perfusion of cardioplegic solution was non-uniformly distributed to the regional and transmural wall of normal pig hearts. Absence of functional correlation was a limitation of this study. However, these findings suggest that inadequate protection of the ventricular septum by antegrade cardioplegia might be an explanation for the abnormalities of septal wall motion after open-heart surgery.

Positron emission tomography and low-dose dobutamine echocardiography in the prediction of postrevascularization improvement in left ventricular function and exercise parameters

BACKGROUND

We studied the value of low-dose dobutamine echocardiography (LDDE) and positron emission tomography (PET) in predicting improvement of left ventricular function and exercise parameters after revascularization.

METHODS

Forty-six consecutive patients with ischemic heart disease and an ejection fraction (EF) of 35% +/- 7% were included. Before revascularization, the patients underwent exercise testing and myocardial viability testing by LDDE and fluoride 18-fluoro-2-deoxyglucose PET. Six months after revascularization they underwent coronary angiography to study graft patency, and echocardiographic examination and the exercise test were repeated.

RESULTS

In the prediction of the presence or absence of improved postrevascularization function in left ventricular regions with patent grafts, PET was more sensitive than LDDE (42/52 regions [81%] vs 27/52 regions [51%], P <.01), whereas LDDE was more specific than PET (187/209 regions [89%] vs 118/209 regions [56%], P <.001). Improvement of regional myocardial dysfunction was found in 19 patients, but their global left ventricular function did not improve significantly (EF 34% +/- 6% and 36% +/- 7%). In the remaining 27 patients with irreversible dysfunction, EF decreased (EF 36% +/- 7% vs 32% +/- 8%, P <.05). Among patients with reversible myocardial dysfunction, the rate pressure product (RPP) increased after revascularization (19,522 +/- 5474 vs 26,190 +/- 5610 mm Hg/min, P <.01), whereas the RPP did not change in patients with irreversible myocardial dysfunction (21,546 +/- 5450 and 22,774 +/- 8249 mm Hg/min). The number of PET viable segments was a predictor of the postoperative increase in the RPP in univariate (P <.04) and multivariate analyses (P <.001). In contrast, LDDE did not bear any prognostic information about improvement in the RPP.

CONCLUSIONS

This study confirms earlier findings of higher sensitivity and lower specificity of PET compared with LDDE in predicting improvement of regional left ventricular function after revascularization. However, the feasibility of predicting postrevascularization improvement of exercise parameters seems unique for PET. The potential prognostic value of this finding needs further investigation.

Left ventricular aneurysmectomy in patients with poor left ventricular function

Physical performance and left ventricular (LV) function in the resting state were assessed in 22 patients with postinfarction anterior-apical left ventricular aneurysm (LVA) and global ejection fraction less than or equal to 20% who subsequently underwent radical LVA resection. The basic findings in the 20 survivors of surgery were significant improvement of global systolic LV function and more or less complete recovery of regional ejection fraction in the predominantly viable low and high lateral LV wall. This improvement was evident in patients with concomitant bypass grafting as well as in those with isolated and ungraftable lesions of the left anterior descending (LAD) coronary artery. We conclude that postinfarction anterior-apical LVA in a poorly functioning LV is suitable for surgical treatment, which can be accomplished with acceptable risk. All graftable stenotic major coronary arteries should be bypassed, in addition to the LVA resection, but a minority of patients with isolated, ungraftable LAD disease are likely to benefit from aneurysmectomy alone.

Revascularization of infarcted vs. viable myocardium. Effects on symptoms, physical performance and global/regional left ventricular function

Symptoms, physical performance and global vs. regional left ventricular (LV) function were reviewed in 25 patients with postinfarction anterior-apical akinesia and minor dyskinesia who subsequently underwent revascularization of all graftable stenotic vessels. The observed postoperative improvement in functional NYHA capacity and physical performance was not related to significant change in any systolic or diastolic variable of global LV function. 'Nonspecific postoperative septal hypokinesia' developed in most cases. The regional ejection fraction showed slight (nonsignificant) mean increase in the infarcted apex and low anterior wall supplied by the left anterior descending artery, but marked increase in the noninfarcted lateral wall supplied by the left circumflex branch. Hearts with grafted left circumflex artery showed on average lower preoperative and postoperative ejection fraction in the lateral wall than did hearts without such grafting, but the rise in regional ejection fraction was significant only after left circumflex grafting. The clinical response to coronary artery surgery is attributed mainly to functional improvement of non-infarcted myocardium. Revascularization of viable myocardium occurs directly via bypass grafts, but collateral vessels may also contribute.

Enhanced regional left ventricular function after distant coronary bypass by means of improved collateral blood flow

To determine whether coronary artery bypass surgery can improve function in left ventricular regions not amenable to direct revascularization, 24 patients with multivessel coronary artery disease were studied by radionuclide angiography and coronary arteriography before and 6 months after coronary artery bypass surgery. All had proximal stenosis of the left circumflex artery or a major obtuse marginal branch. Left ventricular regional function was assessed by dividing the left ventricular region of interest into 20 sectors; the 8 sectors corresponding to the posterolateral free wall were used to assess function in the left circumflex artery distribution. Change in function in the left anterior descending territory was not analyzed because of the non-specific septal hypokinesia that develops postoperatively. For the total group, coronary artery bypass surgery significantly increased both global left ventricular ejection fraction during exercise (43 +/- 13% to 50 +/- 14%, p less than 0.001) and the change in ejection fraction from rest to exercise (-7 +/- 10% to 0 +/- 6%, p less than 0.001). Such improvement was observed in 9 of 10 patients with all stenoses bypassed, and to an equivalent degree in 9 of 10 patients in whom the left circumflex artery either could not be bypassed or the bypass graft was occluded (but bypass grafts to other coronary arteries were patent). Similarly, regional ejection fraction in posterolateral segments during exercise also increased comparably after operation in patients with a patent (from 57 +/- 18% to 70 +/- 19%, p less than 0.001) or nonpatent (from 51 +/- 14% to 68 +/- 14%, p less than 0.001) left circumflex graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of coronary artery surgery on left ventricular performance, segmental wall movement, and exertional ischaemia

The effects of coronary artery surgery on left ventricular performance were assessed serially by echocardiography and treadmill exercise testing in 54 patients. Patients were assessed one day before operation and again before patients left hospital (mean 10 days after operation) and one month and six months after operation. At the predischarge assessment, 41 (77%) patients showed new abnormalities of left ventricular segmental wall movement, chiefly anteroseptal hypokinesia with hyperkinesia of the posterolateral segment. Although there were no significant changes in anteroseptal wall thickening after operation, there was a significant increase in posterior wall thickening at all postoperative assessments. The frequency of this abnormality decreased progressively after operation; it persisted in 19 (35%) patients at six months. Left ventricular fractional shortening decreased after operation and at one month was significantly less than before operation. There were no significant changes in left ventricular diastolic diameter during the study. Haemodynamic function during exercise, the duration of exercise, and features of reversible myocardial ischaemia all improved progressively and significantly after coronary artery surgery. Abnormalities in left ventricular segmental wall movement and thickening commonly develop early after coronary artery surgery but tend to resolve by six months and do not seem to impair left ventricular contractility at rest or exercise performance and haemodynamic function. Recognition of these echocardiographic changes may be clinically important in the assessment of patients after cardiac surgery.