Clinical Significance of Mitral Annular Calcification
October 30, 2022
By Michael H. Crawford, MD
Professor of Medicine, Lucy Stern Chair in Cardiology, University of California, San Francisco
SYNOPSIS: Researchers found mitral annular calcification to be uncommon, and few experienced associated moderate to severe mitral stenosis or regurgitation. However, the latter group recorded a high mortality rate over three years follow-up, which was significantly lower in those who underwent valve interventions, even when corrected for younger age, fewer comorbidities.
SOURCE: Fukui M, et al. Clinical outcomes of mitral valve disease with mitral annular calcification. Am J Cardiol 2022;174:107-113.
Mitral annular calcification (MAC) is uncommon but can be associated with either mitral regurgitation (MR) or mitral stenosis (MS). Because of the challenges of surgical mitral valve replacement with MAC, transcatheter mitral valve replacement (TMVR) is happening more often, but there are few data on the clinical outcomes of MAC or interventions to correct associated MR or MS.
Using the Allina Health echocardiographic database, Fukui et al performed a longitudinal cohort study of MAC patients to obtain long-term outcome data and determine the effects of interventions on the MV. They retrospectively examined the initial echocardiogram of all patients in 2014 and 2015 who experienced moderate or severe MS or MR and had MAC. Researchers excluded those who had undergone other MV procedures. Clinical data were gathered from the medical record through 2018. The primary endpoints were all-cause mortality and a composite of all-cause death or heart failure hospitalization at three years of follow-up. Evidence of MAC was found in 2,855 patients (7% of all echocardiograms). Among these patients, 423 experienced moderate or severe MS or MR but had not undergone a MV procedure (mean age = 80 years; 63% women). Cardiovascular comorbidities were common in these patients: hypertension (90%), dyslipidemia (63%), chronic kidney disease (56%), coronary artery disease (54%), and atrial fibrillation (50%). Moderate or severe MR was present in 67%, MS in 22%, and both in 11%. MAC exclusively involved the posterior annulus in almost all patients. The leaflets and subvalvular apparatus were affected commonly (98% and 60%, respectively), especially in those with MS.
Over the three-year follow-up period, all-cause death was 46%, heart failure hospitalizations were 46%, and the combination was 68%. Overall, 14% underwent a MV intervention: 6% surgical valve replacement, 4% surgical valve repair, 3% transcatheter edge to edge repair, and less than 1% balloon valvuloplasty. The 30-day mortality rate for those who underwent an intervention was 5%. The patients who did not undergo an intervention recorded a higher all-cause mortality rate (HR, 2.80; 95% CI, 1.60-4.92; P < 0.001) as well as a higher composite outcome (HR, 1.43; 95% CI, 1.00-2.04; P = 0.05) than those who did undergo an intervention. Also, the survival rate at the three years follow-up point was much higher among those who underwent an intervention vs. those who did not (78% vs. 50%; P < 0.001). Those who underwent an intervention were younger and more often experienced severe symptomatic MR, but the survival advantage of intervention persisted after multivariate adjustment. The authors concluded about 7% of echocardiograms will exhibit MAC, and those with associated moderate-to-severe MS or MR record a poor survival rate. A corrective intervention might ameliorate that low rate.
COMMENTARY
This retrospective, longitudinal database study confirms MAC is found in 5% to 10% of unselected echocardiograms and is largely a disease of older women. Fukui et al focused on those with moderate-to-severe associated MR and MS, which was found in only 1% of the echocardiograms (or 14% of those with MAC). These patients recorded a remarkably high three-year mortality rate (46%) and an identical rate of heart failure hospitalizations. In addition, interventions to correct the moderate-to-severe MR or MS were infrequent (14%) and usually surgical. However, those who did undergo an intervention recorded a much lower mortality rate over three years (22% vs. 50%), which was statistically significant — even when adjusting for younger age and fewer comorbidities found in the intervention group compared to those who did not undergo an intervention. Thus, the authors concluded efforts to improve interventions for this group, such as TMVR (no one in this study underwent this procedure), are worthwhile.
There were several weaknesses. There is the selection bias of those undergoing an echocardiogram, so the population does not represent everyone with MAC, but it probably represents most of those with associated moderate-to-severe MR or MS. Also, this study was conducted at a single healthcare system, so the characteristics of patients, which were not presented, might not be applicable to other populations. In addition, MAC is challenging to diagnose by echocardiography, so it is possible only the most obvious cases were represented. CT scans would be better for identifying calcium in the mitral annulus, but CT was not used here. Finally, there were no data on procedural complications or the outcome of the MAC patients without moderate-to-severe MS or MR. Most patients who received an intervention underwent surgery vs. transcatheter edge to edge repair (3:1), but none underwent TMVR. Surgery in MAC patients is challenging, and debridement of the annulus can compromise the circumflex coronary artery or result in cardiac rupture. Thus, I agree with the authors that perfecting transcatheter approaches makes sense for these high-risk patients.
Researchers found mitral annular calcification to be uncommon, and few experienced associated moderate to severe mitral stenosis or regurgitation. However, the latter group recorded a high mortality rate over three years follow-up, which was significantly lower in those who underwent valve interventions, even when corrected for younger age, fewer comorbidities.
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