Mitral annular dysjunction in surgical mitral valve prolapse

Funding Acknowledgements

Type of funding sources: None.

Introduction

Mitral valve prolapse (MVP) affects 3% of the population and is the leading indication for mitral valve surgery.[1] Mitral annular disjunction (MAD) is a structural abnormality commonly seen in patients with MVP.[2] MAD is defined as an abnormal separation (>5mm) between the left atrial wall-mitral valve junction and the left ventricle myocardium,[2] associated with hypermobility and myxomatous degeneration of the mitral valve leaflets.[3]  There is a paucity of literature regarding MAD, however evidence is growing that it may be associated with ventricular arrhythmia and sudden cardiac death.[3] We examined the prevalence, imaging characteristics and clinical associations of MAD among patients who have undergone mitral valve surgery for MVP.

Methods

Single centre cohort study of consecutive patients undergoing mitral valve surgery for MVP over a 3-year period. Patient baseline characteristics, echocardiographic parameters, surgical outcomes, frequency of arrhythmic events and 3-year cardiac and all-cause mortality were recorded.  Single site data was obtained from a prospective Australia-wide cardiac surgery registry, as well as retrospective analysis of holter-monitor reports, device interrogation and review of medical records. Transthoracic echocardiogram images were re-examined, and parameters re-measured by a qualified examiner.

Results

Among 73 patients with surgical MVP, 20 patients had MAD (27.4%). The median MAD length was 8.1 (IQR 6.8-11.8) mm. The most severely affected patient had a disjunction length of 28 mm. MAD was associated with younger age at surgery (60 vs 66, P = 0.005), female sex (40.0% vs 22.6%, P = 0.138), bileaflet MVP (50% vs 10.6%, P = 0.004) and less cardiovascular comorbidities, including hypertension (25.0% vs 57.7%, P = 0.013) and hypercholesterolaemia (30.0% vs 61.5%, P = 0.016). Patients with MAD had greater mitral valve leaflet lengths, mitral annular diameters, and high-velocity systolic signal on tissue doppler of the mitral valve annulus (pickelhaube sign). Three patients in the MAD positive group had an arrhythmic event (VF or VT) at 3 years compared to one in the MAD negative group. There was no significant difference in 3-year cardiac or all-cause mortality between groups.

Conclusion

MAD is a common anatomical abnormality in patients with surgical MVP, and is easily detected on transthoracic echocardiography. It is associated with younger age at surgery, female sex, bileaflet MVP, increased leaflet length and annulus diameter. There was a signal towards increased arrhythmic events in patients with MAD despite younger age and less cardiovascular risk factors. Large longitudinal studies are needed to further assess the association of MAD with arrhythmic events to help guild appropriate investigation and risk stratification of these patients. Abstract Figure. MAD on Parasternal Long axis view  Abstract Figure. Pickelhaube sign

Operative Outcomes with Myxomatous Mitral Valve Repair: Experience with 586 Patients

INTRODUCTION

American Heart Association (AHA) guidelines recommend mitral valve repair for myxomatous mitral regurgitation whenever possible to prevent LV dysfunction and early mortality. Here we review our early operative outcomes with mitral valve repair for myxomatous mitral regurgitation.

METHODS

We collected data from 586 consecutive patients that underwent mitral repair for myxomatous disease at the Prince Henry and Prince of Wales Hospitals Sydney between 1997 and 2012. All patients had pre- and postoperative transthoracic echocardiograms.

RESULTS

In the first 30 days postoperatively there were five deaths (0.9%), four strokes (0.7%) and five transient ischaemic attacks (TIAs) (0.9%). Repair involved resection in 55.5%, neochordal reconstruction in 41.6%, and in 2.9% a combination of both. There was increasing use of neochordae since 2006. At discharge 99% had mitral regurgitation (MR) ≤ mild and ≤ trivial in 79.5%. For posterior leaflet disease neochordae had improved MR at discharge compared with resection (85% vs 78%, P<0.05). Preoperative triscupid regurgitation (TR) and pulmonary hypertension > mild were associated with a greater degree of MR at discharge (P<0.05) for reasons that are unclear.

CONCLUSION

We have shown excellent early results for mitral repair with very low operative mortality and excellent freedom from significant MR. Successful mitral repairs with low morbidity have resulted in a pattern of early referral in keeping with the current guidelines.

Lp(a) and conventional risk profiles predict the severity of coronary stenosis in high-risk hospital-based patients

AIMS

To explore predictive power of Lp(a), of conventional lipoprotein profiles and their carrier proteins, and of biometric measurements, for the presence and severity of angiographically documented coronary disease in high-risk patients, and to compare risk profiles in men and women.

METHODS

We determined coronary artery disease (CAD) risk factors in 1308 Australian Caucasian patients (313 women and 995 men) aged < or =65 years who consecutively underwent coronary angiography.

RESULTS

In univariate analyses of the risk factors, lipid profiles, Lp(a), cigarette smoking, diabetes, hypertension and obesity were all higher in men and women with CAD and changed significantly with the number of significantly diseased vessels (> or =50% luminal obstruction). When stepwise logistic regression analysis was applied, age (OR 1.06, 95% CI: 1.04-1.09), TC/HDL-C (OR 1.29, 95% CI: 1.15-1.45), male gender (OR 2.64, 95% CI: 1.67-4.16), hyperLp(a) (> or =300 mg/L) (OR 2.09, 95% CI: 1.42-3.07), lifetime smoking dose (OR 1.02, 95% CI: 1.01-1.03), diabetes (OR 2.19, 95% CI: 1.14-4.18) and waist/hip ratio (OR 14.53, 95% CI: 1.21-174.90) were predictive of the disease. Both Lp(a) levels and percentage of hyperLp(a) increased linearly with the number of significantly diseased vessels. When the analyses were conducted in men and women separately, hyperLp(a), TC/HDL-C, lifetime smoking dose and age remained as significant predictors in both groups but the waist/hip ratio was only predictive in women.

CONCLUSIONS

As Lp(a) is an independent predictor of the occurrence and extent of coronary stenosis and relevant to treatment options, we suggest that it should be measured routinely in the coronary risk profile assessment of high-risk patients.

Relationship between total plasma homocysteine, polymorphisms of homocysteine metabolism related enzymes, risk factors and coronary artery disease in the Australian hospital-based population

Modest elevations of circulating homocysteine are common in patients with vascular disease. We explored interrelations between total plasma homocysteine levels and mutations in genes for three key enzymes in methionine-homocysteine metabolism. Methyltetrahydrofolate reductase (MTHFR) 677C-->T, cystathionine beta synthase (CBS) 68-bp insertion at exon 8, and methionine synthase (MS) 2756A-->G were typed in 685 Australian caucasian patients aged < or =65 years with and without angiographically documented coronary artery disease (CAD). We also assessed associations between homocysteine levels and extracellular superoxide dismutase (EC-SOD) and other CAD risk factors. There were significant correlations between plasma total homocysteine, and EC-SOD (r = 0.170, p = 0.001 for men; r = 0.241, p = 0.003 for women) and LDL (r = 0.153, p = 0.001 for men; r = 0.132, p = 0.081 for women). Levels were also significantly higher among patients with unstable angina (15.30+/-0.44 micromol/l for men, 14.44+/-0.74 micromol/l for women) than those without angina (13.98+/-0.38 micromol/l for men, 13.41+/-0.98 micromol/l for women) or with stable angina (14.00+/-0.37 micromol/l for men, 12.88+/-0.71 micromol/l for women). There were no significant associations between the levels and the presence or severity of CAD. The mutant MTHFR homozygotes tended to have higher levels and those with the MS and CBS mutations tended to have lower levels. We conclude that there is a significant correlation between plasma homocysteine levels and EC-SOD suggesting that elevated homocysteine may exert oxidative stress and that levels are associated with unstable angina, but not the occurrence or extent of coronary stenosis. The contributions to total plasma homocysteine levels of the common mutations of genes coding for the enzymes controlling homocysteine metabolism are modest.

The frequency of a common mutation of the methionine synthase gene in the Australian population and its relation to smoking and coronary artery disease

BACKGROUND

Modest elevations in levels of circulating homocysteine are common in patients with vascular disease. Methionine synthase is a vitamin B12-dependent enzyme catalysing the re-methylation of homocysteine to methionine; reduced methionine synthase activity results in elevated level of homocysteine.

DESIGN

A case-control study.

METHODS

We explored the frequency and distribution of a 2756A-->G (D919G) mutation of the methionine synthase gene, detected by polymerase chain reaction genotyping, in 745 Australian Caucasian patients aged < or = 65 years (550 men and 195 women) with and without angiographically documented coronary artery disease (CAD).

RESULTS

The frequency distributions of AA, AG and GG genotypes were 61.9%, 33.8% and 4.3%, respectively, and were in Hardy-Weinberg equilibrium. There was no correlation between the methionine synthase mutation and CAD from simple chi2 comparison. However, the interactive term of life-time smoking dose with methionine synthase genotypes was predictive of both the number of significantly diseased vessels (> or =50% luminal obstruction; chi2 = 12.518, P=0.0019), and the presence or absence of significant CAD (chi2=7.045, P=0.027). A stepwise logistic regression analysis showed that smokers who were also GG homozygotes had more severe CAD compared with smokers of other genotypes. The methionine synthase genotypes were not associated with any of the other established CAD risk factors assessed in our study.

CONCLUSIONS

We conclude that the methionine synthase 2756A-->G mutation is common, with homozygosity occurring in approximately 4% of white Australians, and that it has an interactive effect with life-time smoking dose to increase the severity of CAD. Smokers who are also GG homozygotes have additionally elevated CAD risk.

Aortoiliac imaging by projective phase sensitive MR angiography: effects of triggering and timing of data acquisition on image quality

To assess the ability of projective phase sensitive magnetic resonance (MR) angiography to visualize the aortoiliac vascular segment, and to determine the effects of triggering and timing of data acquisition om image quality, we studied 18 healthy volunteers, mean age 33.3 +/- 11 years, by color Doppler imaging and by MR angiography. MR angiography was performed at 1.5 T using a flow-adjustable gradient-echo (FLAG) sequence operated in both ECG-triggered and non-triggered acquisition modes. The images were graded in a blinded fashion by two independent observers. The data were analyzed using Pearson's chi-square analysis. Eighteen triggered time-resolved and 17 non-triggered, time-averaged MR angiograms consisting of 252 and 17 angiographic images, (AI) respectively, were analyzed. In the triggered mode 69 (27.4%) AI and in the non-triggered mode 2 (11.8%) AI were diagnostic. At least one triggered diagnostic AI was obtained in each subject. The image grades were not statistically different between observers (kappa = 0.6686). In the triggered mode diagnostic images were acquired within +/- 90 msec of the peak systolic flow velocity determined by Doppler. The proportion of diagnostic images in the triggered mode was highest (73.3%) within a 30-msec interval before the peak flow. In healthy subjects the aortoiliac segment is reliably visualized by FLAG MR angiography. The optimum results are achieved using the triggered acquisition mode and timing acquisition to the initial 180 msec of the abdominal aortic systolic flow pulse.

Assessment of myocardial infarct size by means of T2-weighted 1H nuclear magnetic resonance imaging

Proton (1H) nuclear magnetic resonance (NMR) imaging is thought to depict zones of recent myocardial infarction in contrast to noninfarcted myocardium. This is related to T2 increases in infarct zones that have been verified previously by relaxometry measurements in excised myocardial samples. Accordingly the present study was undertaken to evaluate a 1H NMR imaging method to optimize T2 contrast and measure infarct size in a high-field imaging system (1.5 T). To accomplish this, NMR images were acquired every other R wave with echo times of 30 and 100 msec. The first echo image was used for myocardial border definition and the second echo image, which highlighted the myocardial infarction, for infarct border definition. This T2-weighted approach yielded a significant correlation between infarct size by NMR and pathologic methods. However, NMR imaging tended to overestimate infarct size, and the NMR image depicted abnormal signal well beyond the extent of the pathology-determined infarct. There was a significant relationship between NMR-imaged infarct size and myocardial mass with microsphere-determined reduction in blood flow of 25% or more. These data suggest that T2-weighted NMR imaging depicts not only infarct but also some reversibly injured myocardium.