While mitral regurgitation (MR) is still fairly rare, the population is growing along with the aging Baby Boomer generation. The guideline-recommended treatment is fairly well established in patients with symptomatic MR, but those with asymptomatic disease have a less clear strategy, and some surgeons are now advocating for earlier intervention in this population.
Mitral regurgitation is becoming increasingly prevalent in the older population. The U.S. prevalence of moderate to significant MR—
although often under-diagnosed—is between two and three million patients and is expected to increase to five million by 2030. Patients with comorbidities have a greater prevalence of MR. Specifically, chronic ischemic MR occurs in approximately 20 to 25 percent of patients followed after MI and in 50 percent of those with post-infarct congestive heart failure (Eur J Cardiothorac Surg 2010;37:170-185).
While the ACC/AHA guidelines continue to base Class I designations on myocardial dysfunction, or rescue strategy, some surgeons advocate for earlier surgical intervention.
"MR is increasingly prevalent in the aging population, and may lead to substantial all-cause morbidity and mortality, particularly in those with heart failure," says Vinay Badhwar, MD, a cardiothoracic surgeon at Central Florida Cardiac & Vascular Institute in Orlando. "Timely surgical referral of these patients is truly important for improved clinical outcomes."
Specifically, the ACC/AHA guidelines focus on mitral repair for asymptomatic MR, reserving Class I indications for left ventricular (LV) ejection fraction of 30 to 60 percent and an end-systolic dimension of more than 40 mm. Class IIa indications include a normal LV with demonstrable complications (J Am Coll Cardiol 1998;32:1486-1588).
"Asymptomatic or minimally symptomatic patients may represent the optimal condition for early surgical valve restoration to maximize early and late outcomes," says Davis C. Drinkwater, Jr., MD, cardiothoracic surgeon at HCA's Centennial Medical Center in Nashville, Tenn.
Drinkwater suggests the expansion of surgery to asymptomatic patients should be predicated on myocardial accommodation (i.e., atrial or ventricular enlargement) to defective valves that may sustain patients in an asymptomatic state for years, and may have profound long-term effects; and improved outcomes with valve repair in high-volume centers.
If a patient is asymptomatic with severe MR, Badhwar recommends that he or she should be followed until the ventricular end-diastolic dimension is greater than 40 mm or he or she develops pulmonary hypertension or any other structural sign of deterioration of the heart, such as atrial fibrillation or right/left atrial enlargement.
"Even in asymptomatic patients without other risk factors, medical management of severe mitral regurgitation carries a two-fold increase in sudden death, about 0.8 percent per year," Drinkwater says. Repair is characterized by low mortality and long-lasting durability, with the 10-year reoperation-free survival rate ranges between 93 and 96 percent (J Thorac Cardiovasc Surg 1998;116:734-743).
One study, which compared early surgical intervention with watchful waiting for 447 asymptomatic patients with severe MR, found that the estimated actuarial seven-year cardiac mortality was 0 percent in the operated arm and 5 percent in the conventional treatment arm (Circulation 2009;119:797-804). Kang et al concluded that early surgery is associated with more improved long-term clinical outcomes than the conventional treatment strategy via a decrease in cardiac mortality and congestive heart failure hospitalization.
"Early repair of mitral regurgitation can result in recovery of ventricular function and restoration of normal life expectancy," Badhwar concludes. "Of course, early intervention is dependent on early diagnosis and referrals, which is why increased understanding of the disease is required on the primary care level."