Indications for valve surgery in asymptomatic patients with aortic and mitral stenosis

Aortic valve replacement for patients with mild to moderate aortic stenosis undergoing coronary artery bypass surgery

Aortic valve replacement (AVR) is not normally recommended in asymptomatic patients, even if aortic stenosis is severe. However, as the population ages, an increasing number of patients with mild or moderate aortic stenosis will require coronary artery bypass grafting (CABG). In these cases, risk of "prophylactic" AVR needs to be weighed against risks of subsequent worsening of the mildly or moderately diseased aortic valve. If unoperated, aortic stenosis will worsen at an average of 6-8 mmHg per year (-0.1 cm2/year valve area), and one-quarter of such patients will require late AVR with a high operative mortality (14-24%). If AVR is performed at the time of CABG, operative risk is increased only slightly (from 1-3% to 2-6%), as are late mortality (1-2% per year) and morbidity (1-2% per year), mainly from hemorrhagic complications. Intrinsic gradients of most prosthetic valves are sufficiently low that even patients with low aortic valve gradients are likely to derive hemodynamic benefit from AVR. Thus, if there is a measurable (>20-25 mmHg) gradient across the aortic valve in a patient who requires CABG, the patient is at considerable risk for developing symptomatic aortic stenosis prior to reaching the end of expected benefit from CABG; in this case AVR should be considered. It may be reasonable in patients with very mild gradients (<25 mmHg) to defer aortic valve surgery; however, it should be noted that aortic stenosis progression is generally more rapid when the initial gradient is small.

Should coronary artery bypass graft surgery patients with mild or moderate aortic stenosis undergo concomitant aortic valve replacement?

OBJECTIVES

This study utilizes Markov decision analysis to assess the relative benefits of prophylactic aortic valve replacement (AVR) at the time of coronary artery bypass graft surgery (CABG). Multiple sensitivity analyses were also performed to determine the variables that most profoundly affect outcome.

BACKGROUND

The decision to perform CABG or concomitant CABG and AVR (CABG/AVR) in asymptomatic patients who need CABG surgery but have mild to moderate aortic stenosis (AS) is not clear-cut.

METHODS

We performed Markov decision analysis comparing long-term, quality-adjusted life outcomes of patients with mild to moderate AS undergoing CABG versus CABG/AVR. Age-specific morbidity and mortality risks with CABG, CABG/AVR, and AVR after a prior CABG were based on the Society of Thoracic Surgeons national database (n = 1,344,100). Probabilities of progression to symptomatic AS, valve-related morbidity, and age-adjusted mortality rates were obtained from available published reports.

RESULTS

For average AS progression, the decision to replace the aortic valve at the time of elective CABG should be based on patient age and severity of AS measured by echocardiography. For patients under age 70 years, an AVR for mild AS is preferred if the peak valve gradient is >25 to 30 mm Hg. For older patients, the threshold increases by 1 to 2 mm Hg/year, so that an 85-year-old patient undergoing CABG should have AVR only if the gradient exceeds 50 mm Hg. The AS progression rate also influences outcomes. With slow progression (<3 mm Hg/year), CABG is favored for all patients with AS gradients <50 mm Hg; with rapid progression (>10 mm Hg/year), CABG/AVR is favored except for patients >80 years old with a valve gradient <25 mm Hg.

CONCLUSIONS

This study provides a decision aid for treating patients with mild to moderate AS requiring CABG surgery. Predictors of AS progression in individual patients need to be better defined.

Cardiac disease and pregnancy

The pregnant state imposes a supraphysiologic strain on the pregnant woman's cardiac performance through complex biochemical, electric, and physiologic changes affecting the blood volume, myocardial contractility, and resistance of the vascular bed. In the presence of underlying heart disease, these changes can compromise the woman's hemodynamic balance, her life, and that of her unborn child. Cardiac pathology represents a heterogeneous group of disorders, each with its own hemodynamic, genetic, obstetric, and social implications. Physicians caring for these women should actively address the issue of reproduction. Ideally, pregnancy should be planned to occur after optimization of cardiac performance by medical or surgical means. Once pregnancy is achieved, the concerted effort of a multidisciplinary team of obstetricians, cardiologists, anesthesiologists, nursing, social, and other services provides the best opportunity to carry the pregnancy to a successful outcome.

Valvular heart disease. Identifying and managing mitral and aortic lesions

Evaluation and treatment of valvular heart disease (table 1) are in evolution. Echocardiography is the principal diagnostic tool. In general, mitral and aortic stenotic lesions warrant surgical treatment when symptoms appear. Such intervention is also indicated in symptomatic patients with a regurgitant mitral or aortic lesion. Some patients with regurgitant lesions require surgical treatment even before the onset of symptoms, such as when left ventricular dysfunction or dilatation supervenes. Surgical treatment of valvular lesions consists of repair or replacement, except in the case of mitral stenosis, where PBMC is a reasonable alternative. In general, medical therapy has a very limited role in the treatment of valvular heart disease. Severe aortic insufficiency is an exception. In such cases, afterload reduction has proved beneficial in the long-term prognosis.

Surgical treatment of oligosymptomatic mitral valve incompetence?

OBJECTIVE

Despite improvements of the surgical technique in NYHA (III)-(IV) mitral valve incompetence (MVI) postoperative long-term results remain poor. As long-term results reflect primarily the ventricular function rather than the quality of the surgical technique the contractile performance of isolated papillary muscles obtained from patients undergoing mitral valve replacement for MVI (n = 25) was analysed in detail.

METHODS

Muscle preparations (0.4 x 5.0 mm) obtained from left ventricular papillary muscles (NYHA (I), n = 4; NYHA (II), n = 7; NYHA (III), n = 8; NYHA (IV), n = 6) were loaded for intracellular calcium measurements with FURA-2, stretched to optimal length (Lmax) and electrically stimulated with frequencies ranging from 30 to 180 beats/min (b.p.m.) (10% above threshold, 37 degrees C, Krebs-Henseleit solution). Isometric force development and diastolic intracellular calcium (measured by the 'ratio method'; excitation light: wavelengths alternating 340 and 380 nm, frequency: 250 Hz) were simultaneously recorded as a function of the stimulation frequency.

RESULTS

At 60 b.p.m. force development was significantly higher in NYHA (I) myocardium (21.3 +/- 2.8 mN/mm2) than in NYHA (III) myocardium (12.8 +/- 2.2 mN/mm2), (P < 0.0001). In NYHA (I) myocardium force rose with increasing stimulation frequency ('positive staircase'). In contrast the stimulation frequency associated with maximum force was shifted towards lower frequencies in NYHA (II)-(IV) myocardium ('negative staircase'). As compared with NYHA (I) myocardium diastolic intracellular calcium was significantly elevated at 150 b.p.m. in NYHA (II)-(IV) myocardium (P < 0.01).

CONCLUSION

The data show, that severe impairment of contractile function ('negative staircase phenomenon', reduced force, elevated diastolic calcium) is present in MVI classified as NYHA (III)-(IV) that may explain the poor long-term results. Most interestingly the data argue for a significant impairment of myocardial function even in NYHA (II) MVI. The results suggest an early surgical treatment of mitral valve incompetence as long as the myocardial function is normal (NYHA (I)) as (1) a reduced perioperative risk, (2) improved long-term results, and (3) a higher probability for mitral valve repair (instead of replacement) may be expected in these early stages of mitral valve disease.

The natural history and rate of progression of aortic stenosis

One of the challenges in clinical cardiology is to determine the optimal time of valve replacement surgery in patients with aortic stenosis. To meet this challenge, one requires an accurate knowledge of the natural history and rate of progression of the disease. This review will summarize the natural history of aortic stenosis in terms of symptoms, mortality, and stenosis progression.