Coronary artery bypass surgery with or without mitral valve annuloplasty in moderate functional ischemic mitral regurgitation: final results of the Randomized Ischemic Mitral Evaluation (RIME) trial

Surgical options for the management of ischemic cardiomyopathy

OPINION STATEMENT

Novel surgical alternatives and the refinement of conventional surgical therapies for the treatment of ischemic cardiomyopathy are in constant evolution. Current approaches involve the determined application of the appropriateness criteria for CABG surgery, the extension of mitral valve repair to complex patients with ischemic cardiomyopathy, finding appropriate patients who might benefit from surgical ventricular reconstruction, and surgical attempts to regenerate lost or damaged myocardium with transplanted stem cells. The refinement of surgical techniques and the medical optimization of candidates for surgery remain a cornerstone of management for patients with complex heart disease like ischemic cardiomyopathy. The horizon is bright for patients suffering from this condition and concentrated research efforts by groups such as the NHLBI-sponsored Cardiothoracic Surgery Network will have a major impact on the future of patients with heart disease.

Coronary artery bypass grafting in patients with left ventricular dysfunction: predictors of long-term survival and impact of surgical strategies

BACKGROUND

In the surgical management of ischemic cardiomyopathy, factors associated with long-term prognosis after coronary artery bypass grafting (CABG) in patients with severe left ventricular (LV) dysfunction are poorly understood. This study aimed to determine predictors of clinical outcomes in patients with severe LV dysfunction undergoing CABG.

METHODS

Out of 6084 patients who underwent CABG between 1997 and 2011, 476 patients (aged 62.6 ± 9.3 years, 100 females) were identified as having severe LV dysfunction (ejection fraction ≤ 35%), preoperatively. All-cause mortality and adverse cardiac events (myocardial infarction, repeat revascularization, stroke and hospitalization due to cardiovascular causes) were evaluated during a median follow-up period of 55.2 months (inter-quartile range: 26.4-94.8 months).

RESULTS

During the follow-up, 187 patients (39.3%) died and 126 cardiac events occurred in 104 patients (21.8%). Five-year survival and event-free survival rates were 72.1 ± 2.2% and 61.3 ± 2.4%, respectively. On Cox-regression analysis, old age (P < 0.001), recent MI (P < 0.001), history of coronary stenting (P = 0.023), decreased glomerular filtration rate (P < 0.001), and presence of mitral regurgitation (≥moderate) (P = 0.012) or LV wall thinning (P = 0.007) emerged as significant and independent predictors of death. After adjustment for important covariates affecting outcomes, none of the pump strategy (off-pump vs. on-pump), concomitant mitral surgery or surgical ventricular reconstruction (SVR) affected survival or event-free survival (P = 0.082 to >0.99).

CONCLUSIONS

Long-term survival following CABG in patients with severe LV dysfunction was affected by age, renal function, recent MI, prior coronary stenting, and presence of mitral regurgitation or LV wall thinning. Neither concomitant mitral surgery nor SVR, however, had significant influence on clinical outcomes.

Effect of systematic downsizing rigid ring annuloplasty in patients with moderate ischemic mitral regurgitation

OBJECTIVE

Functional ischemic mitral regurgitation (FIMR) increases mortality independently of the baseline characteristics and ventricular function. The effect of treating FIMR with annuloplasty is unclear when mitral regurgitation is moderate. Myocardial revascularization alone has been shown to improve mitral valve function.

METHODS

We randomized 31 patients with moderate (grade 2-4) FIMR to receive either coronary artery bypass grafting (CABG) alone or CABG plus downsizing mitral ring annuloplasty. The patients were followed up for clinical outcomes and echocardiographic assessment of mitral valve function and left ventricular dimensions at 3 and 12 months. Clinical improvement was assessed using the Minnesota quality-of-life questionnaire, 6-minute walk test, and brain natriuretic peptide levels.

RESULTS

The clinical course was similar in the 2 groups of patients during the study period. FIMR was perfectly corrected intraoperatively in the ring group. Echocardiographic follow-up at 3 months showed no difference in the FIMR grade between the 2 groups (66% less than grade 2 in the CABG alone and 86% in the CABG plus ring group; P = .316). The improvement in the CABG alone group was even more marked at 12 months (85% less than grade 2 in the CABG group and 85% in the CABG plus ring group). The left ventricular ejection fraction was significantly better at 3 months in the CABG alone group, although at 12 months, the left ventricular ejection fraction in the 2 groups had improved similarly.

CONCLUSIONS

Although initially effective at reducing moderate FIMR, the addition of a ring did not change the clinical course after CABG surgery. At 12 months, no echocardiographic difference was found in terms of residual mitral regurgitation, left ventricular dimensions and function, or clinical outcomes.

[Mitral regurgitation in heart failure. Surgical therapy]

The optimal treatment of mitral regurgitation concomitant to heart failure remains controversial. A lack of consensus between cardiologists and cardiac surgeons, because of limited studies and heterogeneous data, has led to vaguely defined guidelines and different handling in the clinical routine in the past. However, progress in the operative management with excellent results of individual experienced centers suggests that a variety of patients might benefit from surgical therapy. Each patient should be evaluated individually regarding the benefits of surgical therapy which requires an interdisciplinary approach ("heart team") due to the complex pathophysiology and demanding diagnostics.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.