Coronary revascularisation in heart failure patients

*For all patients with viable myocardium the three year mortality rate was 8% (80% had CABG). For patients with only fixed scar > 23% mortality rate was 50% (p = 0.018). Only 40% had CABG with no difference in mortality with or without CABG. EF, ejection fraction.

High risk coronary bypass is the most frequent conventional operation in heart failure patients. Incomplete myocardial infarction leaves viable but ischaemic myocardium within involved segments (flow/metabolism mismatch). Hibernating myocardium is an unstable substrate for postinfarction dysrhythmic events and mortality, independent of age or LVEF (event rate 43% v 8% for scar).5 Hibernating myocardium will recover contractile performance with reduced risk of dysrhythmia after coronary revascularisation, but for global improvement in left ventricular function, sufficient reversibly ischaemic territory must be present. DiVerentiation between reversible ischaemia and infarction is made on clinical grounds (angina which responds to sublingual nitrates) and objectively by positron emission tomography (PET) scan or dobutamine stress echocardiography.6 Heart failure patients without reversible ischaemia do not have an improved outlook with coronary bypass, and LVEF alone is a poor predictor of surgical

Figure 11.1. Progressive left ventricular dilatation causes mitral regurgitation and volume overload.

• Cardiac transplantation is a very rare commodity.

• All transplant candidates with coronary disease should be assessed for hibernating myocardium then revascularisation.

• Those candidates with dilated cardiomyopathy should be considered for mitral repair.

• Left anterior descending coronary occlusion causes muscle loss in the apex, septum and anterolateral free wall.

• In 20% of patients cardiac failure occurs within 15 months when the normal elliptical left ventricle loses its apex and becomes spherical.

• The non-infarcted myocardium progressively dilates and further impairs function.

• When more than 50% of the circumference is asynergic surgical left ventricle restoration reduces left ventricular end systolic volume index (LVESVI) to

< 80 ml/m2 and avoids progressive failure.

Table 11.2 Guidelines for coronary bypass versus transplantation in end stage coronary artery disease10

• High risk (5-15% mortality) revascularisation is the treatment of choice for patients with ejection fraction < 20%, reversible ischaemic cardiomyopathy and graftable target vessels.

• Contraindications to coronary bypass are pulmonary artery pressure > 60 mm Hg, right heart failure, and poor target vessels.

CABG

Transplant

Prevailing hibernation Short duration of heart failure Low dose diuretics No right ventricular failure

Stable cardiac output Cardia index > 2.0 l/min/m2 LVEDP < 24 mm Hg Good target vessels First operation

Prevailing scar Prolonged heart failure

High dose diuretics Chronic right ventricular failure

Progressively lower output Cardiac index < 2.0 l/min/m2 LVEDP > 24 mm Hg Poor vessels

Previous revascularisation outcome when compared with the extent of reversible ischaemia.3 7 In fact, survival benefit from coronary bypass increases as LVEF decreases. Other contraindications to high risk coronary surgery are poor target vessels, a pulmonary artery pressure > 60 mm Hg, and significantly impaired right ventricular function.

The ethos for revascularisation of the failing ventricle can be summarised as simplicity, safety, and speed. The intra-aortic balloon pump is employed preoperatively. Only good target vessels to documented reversibly ischae-mic myocardium are grafted to keep the cross clamp time short. Moderate and severe mitral regurgitation are corrected and full thickness scar excised where feasible. Those with access to left ventricular assist devices (LVADs) employ these to keep the perioperative mortality below 10-15%.8 Non-cardiac risk factors for death include great age, female sex, a history of hypertension or chronic obstructive airways disease, and the presence of peripheral vascular disease or renal impairment. In selected patients with hibernating myocardium but poor target vessels to some areas, concomitant transmyocardial laser revascularisation has been shown to improve survival.9

Useful data regarding patient selection and outcome for high risk revascularisation have emerged from transplant centres where end stage heart failure patients were selected out for myocardial revascularisation. Hausmann and colleagues in Berlin compared 225 revascular-ised transplant candidates with 231 others who received a donor organ.10 The important differences between the groups were the longer duration of symptoms, the presence of right heart failure, and a greater incidence of

LVEDP, left ventricular end diastolic pressure.

previous revascularisation in the heart transplant recipients. Operative risk in the coronary bypass group was significantly higher for those with a greatly increased left ventricular end diastolic pressure (LVEDP) (> 24 mm Hg), a low preoperative cardiac output (< 2.0 l/min/ m2), and for patients in NYHA class IV. Hospital mortality was 7.1% for the coronary artery bypass graft (CABG) patients versus 18.2% in the transplant group. There was no significant difference in hospital mortality in patients with LVEF between 10-20% versus those between 20-30%. Survival for the CABG group was 78.9% after six years versus 68.9% in the transplant group. Reinvestigation of CABG patients showed a significant decrease in mean (SD) pulmonary artery pressure from 28.2 (4.7) mm Hg to 21.2 (3.9) mm Hg (p < 0.01). Pulmonary capillary wedge pressure fell from 19.2 (4.3) mm Hg to 13.1 (2.8) mm Hg (p < 0.01). Left ventricular ejection fraction improved from a mean of 0.24 (0.03) to 0.39 (0.06) (p < 0.0001). Others have reported similar findings.11 12 Table 11.2 provides guidelines suggesting coronary bypass in preference to cardiac transplantation for patients with end stage coronary disease. Table 11.3 summarises the surgical treatment options in end stage ischaemic heart disease.

Your Heart and Nutrition

Your Heart and Nutrition

Prevention is better than a cure. Learn how to cherish your heart by taking the necessary means to keep it pumping healthily and steadily through your life.

Get My Free Ebook


Post a comment