Arrhythmic profile, ventricular function, and histomorphometric findings in patients with idiopathic ventricular tachycardia and mitral valve prolapse: clinical and prognostic evaluation

Arrhythmic Mitral Valve Prolapse Syndrome and Ventricular Arrhythmias: A Comprehensive Review and the Role of Catheter Ablation

Mitral valve prolapse (MVP) affects 2-3% of the general population, and despite its benign prognosis overall, it is associated with sudden death in a small subset of patients. The term "arrhythmic MVP syndrome" (AMVPS) refers to the presence of frequent or complex ventricular arrhythmias, commonly reported in female patients with a stereotypical phenotype including bileaflet myxomatous disease, ECG repolarisation abnormalities in inferior leads, mitral annular disjunction, and significant fibrosis in the inferolateral LV and papillary muscles. Modern imaging technologies have led to the identification of new risk factors that have been implemented in recent risk stratification guidelines; however, screening for patients with MVP who are at risk of sudden cardiac death (SCD) remains challenging. In addition, there is a limited amount of data on the outcomes of different treatment approaches in AMVP and no specific indication for targeted or disease-modifying therapies within current guidelines. Potential arrhythmic substrates in patients with AMVP syndrome have been the subject of interest in previous studies, with areas consisting of fibrosis at the papillary muscle level and the Purkinje system. Premature ventricular contractions (PVCs) originating from these areas have been shown to play an important role as triggers for ventricular fibrillation and SCD in patients with AMVP. Catheter ablation has emerged as a potential treatment modality in patients with MVP and ventricular arrhythmias (VAs), targeting arrhythmic substrates and triggering PVC foci. The aim of this review is to explore the role of catheter ablation in treating patients with AMVP.

Imaging for the assessment of the arrhythmogenic potential of mitral valve prolapse

Mitral valve prolapse (MVP) is the most common valve disease in the western world and recently emerged as a possible substrate for sudden cardiac death (SCD). It is estimated an annual risk of sudden cardiac death of 0.2 to 1.9% mostly caused by complex ventricular arrhythmias (VA). Several mechanisms have been recognized as potentially responsible for arrhythmia onset in MVP, resulting from the combination of morpho-functional abnormality of the mitral valve, structural substrates (regional myocardial hypertrophy, fibrosis, Purkinje fibers activity, inflammation), and mechanical stretch. Echocardiography plays a central role in MVP diagnosis and assessment of severity of regurgitation. Several abnormalities detectable by echocardiography can be prognostic for the occurrence of VA, from morphological alteration including leaflet redundancy and thickness, mitral annular dilatation, and mitral annulus disjunction (MAD), to motion abnormalities detectable with "Pickelhaube" sign. Additionally, speckle-tracking echocardiography may identify MVP patients at higher risk for VA by detection of increased mechanical dispersion. On the other hand, cardiac magnetic resonance (CMR) has the capability to provide a comprehensive risk stratification combining the identification of morphological and motion alteration with the detection of myocardial replacement and interstitial fibrosis, making CMR an ideal method for arrhythmia risk stratification in patients with MVP. Finally, recent studies have suggested a potential role in risk stratification of new techniques such as hybrid PET-MR and late contrast enhancement CT. The purpose of this review is to provide an overview of the mitral valve prolapse syndrome with a focus on the role of imaging in arrhythmic risk stratification. CLINICAL RELEVANCE STATEMENT: Mitral valve prolapse is the most frequent valve condition potentially associated with arrhythmias. Imaging has a central role in the identification of anatomical, functional, mechanical, and structural alterations potentially associated with a higher risk of developing complex ventricular arrhythmia and sudden cardiac death. KEY POINTS: • Mitral valve prolapse is a common valve disease potentially associated with complex ventricular arrhythmia and sudden cardiac death. • The mechanism of arrhythmogenesis in mitral valve prolapse is complex and multifactorial, due to the interplay among multiple conditions including valve morphological alteration, mechanical stretch, myocardial structure remodeling with fibrosis, and inflammation. • Cardiac imaging, especially echocardiography and cardiac magnetic resonance, is crucial in the identification of several features associated with the potential risk of serious cardiac events. In particular, cardiac magnetic resonance has the advantage of being able to detect myocardial fibrosis which is currently the strongest prognosticator.

Determinants of Ventricular Arrhythmias in Mitral Valve Prolapse

BACKGROUND

Mitral valve prolapse (MVP) may be associated with ventricular arrhythmias (VA) even in the absence of significant valvular regurgitation. Curling, mitral annulus disjunction (MAD) and myocardial fibrosis (late gadolinium enhancement [LGE]) may account for arrhythmogenesis.

OBJECTIVES

This study investigated the determinants of VA in patients with MVP without significant regurgitation.

METHODS

This study included 108 patients with MVP (66 female; median age: 48 years) without valve regurgitation. All patients underwent 12-lead electrocardiography, 12-lead 24-hour electrocardiographic Holter monitoring, exercise stress test, and cardiac magnetic resonance. Patients were divided into 2 groups (arrhythmic and no-arrhythmic MVP), according to the presence of VA with a right bundle branch block pattern.

RESULTS

The 62 patients (57%) with arrhythmic MVP showed: 1) higher MAD (median length: 6.0 vs 3.2 mm; P = 0.017); 2) higher prevalence of curling (79% vs 52%; P = 0.012); and 3) higher prevalence of left ventricular LGE (79% vs 52%; P = 0.012). Mediation analysis showed that curling had both a direct (P = 0.03) and indirect effect mediated by LGE (P = 0.04) on VA, whereas the association between MAD and VA was completely mediated by LGE. Patients with severe VA showed more pronounced morphofunctional alterations, in terms of MAD (7.0 vs 4.6 mm; P = 0.004) and presence and severity of curling (respectively, 91% vs 64%; P = 0.010; and 4 vs 3 mm; P = 0.004), compared to those without severe VA.

CONCLUSIONS

In patients with MVP the occurrence of VA with right bundle branch block morphology is the expression of more severe morphologic, mechanical, and tissue alterations. Curling has both a direct and an indirect effect on VA.

Histopathological insights into mitral valve prolapse-induced fibrosis

Mitral valve prolapse (MVP) is a cardiac valve disease that not only affects the mitral valve (MV), provoking mitral regurgitation, but also leads to maladaptive structural changes in the heart. Such structural changes include the formation of left ventricular (LV) regionalized fibrosis, especially affecting the papillary muscles and inferobasal LV wall. The occurrence of regional fibrosis in MVP patients is hypothesized to be a consequence of increased mechanical stress on the papillary muscles and surrounding myocardium during systole and altered mitral annular motion. These mechanisms appear to induce fibrosis in valve-linked regions, independent of volume-overload remodeling effects of mitral regurgitation. In clinical practice, quantification of myocardial fibrosis is performed with cardiovascular magnetic resonance (CMR) imaging, even though CMR has sensitivity limitations in detecting myocardial fibrosis, especially in detecting interstitial fibrosis. Regional LV fibrosis is clinically relevant because even in the absence of mitral regurgitation, it has been associated with ventricular arrhythmias and sudden cardiac death in MVP patients. Myocardial fibrosis may also be associated with LV dysfunction following MV surgery. The current article provides an overview of current histopathological studies investigating LV fibrosis and remodeling in MVP patients. In addition, we elucidate the ability of histopathological studies to quantify fibrotic remodeling in MVP and gain deeper understanding of the pathophysiological processes. Furthermore, molecular changes such as alterations in collagen expression in MVP patients are reviewed.

Late Gadolinium Enhancement of Left Ventricular Papillary Muscles in Patients with Mitral Regurgitation

OBJECTIVE

Arrhythmogenic mitral valve prolapse (MVP) is an important cause of sudden cardiac death characterized by fibrosis of the papillary muscles or left ventricle (LV) wall, and an association between late gadolinium enhancement (LGE) of the LV papillary muscles and ventricular arrhythmia in MVP has been reported. However, LGE of the papillary muscles may be observed in other causes of mitral regurgitation, and it is not limited to patients with MVP. This study was to evaluate the association of LGE of the LV papillary muscles or ventricular wall on cardiac magnetic resonance imaging (CMR) and ventricular arrhythmia in patients with mitral regurgitation.

MATERIALS AND METHODS

This study included 88 patients (mean age ± standard deviation, 58.3 ± 12.0 years; male, 42%) with mitral regurgitation who underwent CMR. They were allocated to the MVP (n = 43) and non-MVP (n = 45) groups, and their LGE images on CMR, clinical characteristics, echocardiographic findings, and presence of arrhythmia were compared.

RESULTS

LV myocardial wall enhancement was more frequent in the MVP group than in the non-MVP group (28% vs. 11%, p = 0.046). Papillary muscle enhancement was observed in 7 (7.9%) patients. Of the 43 patients with MVP, 15 (34.8%) showed LGE in the papillary muscles or LV myocardium, including 12 (27.9%) with LV myocardial wall enhancement and 4 (9.3%) with papillary muscle enhancement. One patient with bilateral diffuse papillary muscle enhancement experienced sudden cardiac arrest due to ventricular fibrillation. Univariable logistic regression analysis showed that high systolic blood pressure (BP; odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09; p = 0.027) and ventricular arrhythmia (OR, 6.84; 95% CI, 1.29-36.19; p = 0.024) were significantly associated with LGE of the papillary muscles.

CONCLUSION

LGE of the papillary muscles was present not only in patients with MVP, but also in patients with other etiologies of mitral regurgitation, and it was associated with high systolic BP and ventricular arrhythmia. Papillary muscle enhancement on CMR should not be overlooked.

Systematic quantification of histologic ventricular fibrosis in isolated mitral valve prolapse and sudden cardiac death

BACKGROUND

Cardiac fibrosis in mitral valve prolapse (MVP) is implicated in the development of sudden cardiac death (SCD); however, the pattern remains poorly characterized.

OBJECTIVE

The purpose of this study was to systematically quantify left and right ventricular fibrosis in individuals with isolated MVP and SCD (iMVP-SCD), whereby other potential causes of death are excluded, compared to a control cohort.

METHODS

Individuals with iMVP-SCD were identified from the Victorian Institute of Forensic Medicine, Australia, and matched for age, sex, and body mass index to control cases with noncardiac death. Cardiac tissue sections were analyzed to determine collagen deposition in the left ventricular free wall (anterior, lateral, and posterior portions), interventricular septum, and right ventricle. Within the iMVP-SCD cases, the endocardial-to-epicardial distribution of fibrosis within the left ventricle was specifically characterized.

RESULTS

Seventeen cases with iMVP-SCD were matched 1:1 with 17 controls, yielding 149 samples and 1788 histologic regions. The iMVP-SCD group had increased left ventricular (anterior, lateral, and posterior; all P <.001) and interventricular septum fibrosis (P <.001), but similar amounts of right ventricular fibrosis (P = .62) compared to controls. In iMVP-SCD, left ventricular fibrosis was significantly higher in the lateral and posterior walls compared to the anterior wall and interventricular septum (all P <.001). Within the lateral and posterior walls, iMVP-SCD cases had a significant endocardial-to-epicardial gradient of cardiac fibrosis (P <.01) similar to other known conditions that cause cardiac remodeling.

CONCLUSION

Our study indicates that nonuniform left ventricular remodeling with both localized and generalized left ventricular fibrosis is important in the pathogenesis of SCD in individuals with MVP.

Mitral valve prolapse and sudden cardiac death: a systematic review and meta-analysis

OBJECTIVES

Mitral valve prolapse (MVP) is commonly observed as a benign finding. However, the literature suggests that it may be associated with sudden cardiac death (SCD). We performed a meta-analysis and systematic review to determine the: (1) prevalence of MVP in the general population; (2) prevalence of MVP in all SCD and unexplained SCD; (3) incidence of SCD in MVP and (4) risk factors for SCD.

METHODS

The English medical literature was searched for: (1) MVP community prevalence; (2) MVP prevalence in SCD cohorts; (3) incidence SCD in MVP and (4) SCD risk factors in MVP. Thirty-four studies were identified for inclusion. This study was registered with PROSPERO (CRD42018089502).

RESULTS

The prevalence of MVP was 1.2% (95% CI 0.5 to 2.0) in community populations. Among SCD victims, the cause of death remained undetermined in 22.1% (95% CI 13.4 to 30.7); of these, MVP was observed in 11.7% (95% CI 5.8 to 19.1). The incidence of SCD in the MVP population was 0.14% (95% CI 0.1 to 0.3) per year. Potential risk factors for SCD include bileaflet prolapse, ventricular fibrosis complex ventricular ectopy and ST-T wave abnormalities.

CONCLUSION

The high prevalence of MVP in cohorts of unexplained SCD despite low population prevalence provides indirect evidence of an association of MVP with SCD. The absolute number of people exposed to the risk of SCD is significant, although the incidence of life-threatening arrhythmic events in the general MVP population remains low. High-risk features include bileaflet prolapse, ventricular fibrosis, ST-T wave abnormalities and frequent complex ventricular ectopy.

TRIAL REGISTRATION

PROSPERO (CRD42018089502).

Mitral valve prolapse and sudden cardiac arrest in the community

BACKGROUND

Mitral valve prolapse (MVP) is relatively common in the general population with recently reported prevalence of 1% and familial clustering (Framingham Heart Study). However, its association with ventricular arrhythmias and sudden cardiac arrest (SCA) remains controversial.

OBJECTIVES

The purpose of this study was to characterize the frequency and clinical profile of patients with MVP who suffer SCA in the community.

METHODS

Patients with SCA cases were prospectively identified in the population-based Oregon Sudden Unexpected Death Study (population ~1 million). The presence of MVP was identified from echocardiograms recorded prior but unrelated to the SCA event. The detailed clinical profile of patients with SCA and MVP was compared with that of SCA patients without MVP to identify potential differences.

RESULTS

A total of 729 SCA patients were evaluated over a 12-year period (mean age 69.5 ± 14.8 years; 64.6% men). MVP was observed in 17 (2.3%) prior to the SCA event (95% confidence interval 1.2%-3.4%). Mitral regurgitation was present in 14 SCA patients with MVP (82.3%) and was moderate or severe in 10 (58.8%). Compared with SCA patients without MVP, SCA patients with MVP were younger (mean age 60.9 ± 16.4 years vs 69.7 ± 14.7 years; P = .02), with fewer risk factors (diabetes 5.9% vs 46.4%; P = .001; hypertension 41.2% vs 78.9%; P = .001) or known coronary disease (29.4% vs 65.6%; P < .001).

CONCLUSION

MVP was observed in a small proportion (2.3%) of SCA patients in the general population, suggesting a low risk overall. Since SCA patients with MVP were characterized by younger age and relatively low cardiovascular comorbidity, a focus on imaging for valve structure/insufficiency as well as genetics could aid future risk stratification approaches.

Imaging of Mitral Valve Prolapse: What Can We Learn from Imaging about the Mechanism of the Disease?

Mitral valve prolapse (MVP) is the most common mitral valve disorder affecting 2%-3% of the general population. Two histological forms for the disease exist: Myxomatous degeneration and fibroelastic disease. Pathological evidence suggests the disease is not confined solely to the valve tissue, and accumulation of proteoglycans and fibrotic tissue can be seen in the adjacent myocardium of MVP patients. MVP is diagnosed by demonstrating valve tissue passing the annular line into the left atrium during systole. In this review we will discuss the advantages and limitations of various imaging modalities in their MVP diagnosis ability as well as the potential for demonstrating extra associated valvular pathologies.

Tissue Doppler echocardiography reveals insufficient contractile reserve recruitment during effort in subjects with mitral valve prolapse and those with thick mitral valve

OBJECTIVE

To assess by tissue Doppler echocardiography (TDE), the tissue velocities, both at rest and after exercise stress testing, in subjects with mitral valve prolapse (MVP) and those with thick mitral valve (TMV).

METHODS

Twenty individuals with typical MVP, 30 with TMV, and 30 healthy controls were enrolled. TDE was performed at the basal-inferior wall and the parameters evaluated were the S, Em, and Am velocities, as well as the Em/Am ratio.

RESULTS

The mean S-wave at rest was higher in subjects with MVP compared to that of the TMV (P < 0.01) and the control groups (P = 0.00005), whereas after exercise it was higher in the control group compared to either MVP (P = 0.013) or TMV group (P = 0.00002). The mean Em wave at rest was higher in the control individuals both at rest (P = 0.007 compared with MVP group and P = 0.013 compared with TMV group), and after exercise (P = 0.0002 and 0.0009, respectively). The Am wave in the MVP group was higher compared with TMV and control subjects at rest (P = 0.022 and 0.00001, respectively) but it was not after exercise (P = ns for both comparisons). The Em/Am ratio of the control group at rest was higher than that of the MVP (P = 0.0000) and TMV (P = 0.00028) groups. However, after exercise, it was higher only when compared with the MVP group (P = 0.016).

CONCLUSIONS

Subjects with MVP and those with TMV exhibit a less effective contractile response to exercise compared to healthy individuals. Some degree of diastolic dysfunction, particularly after exercise, was also detected in the individuals with MVP.

Palpitations: A proper evaluation and approach to effective medical therapy

Palpitations are a common complaint seen in the outpatient setting and the vast majority are benign, although they are occasionally a manifestation of potentially life-threatening conditions. We offer a step-wise guide to the evaluation and management of these patients with the primary goal to identify patients at highest risk for serious arrhythmias. We offer a brief overview of effective management of the varied causes of palpitations.

Occurrence of ventricular late potentials in patients with active acromegaly

OBJECTIVE

Patients with acromegaly have an increased risk of ventricular dysrhythmias and sudden death. Late potentials in a signal-averaged electrocardiogram (SAECG), a predictor of ventricular dysrhythmias, are frequently seen in patients after previous myocardial infarction, but little is known about the prevalence of late potentials in acromegaly. The aim of our study was to investigate the prevalence of late potentials in patients with acromegaly and their relation to the activity of the disease and to myocardial hypertrophy.

PATIENTS

The study included 48 patients with acromegaly [27 males, 21 females, mean age 52.3 +/- 14.2 years, 16 active disease, 32 cured or 'well controlled', under treatment with sandostatin analogues (12/32)] and 38 healthy volunteers as a control group.

RESULTS

Late potentials were detected in 9/16 (56%) patients with active acromegaly vs. 2/32 (6%) with cured/well controlled acromegaly (P = 0.001), defined as normal age-related IGF-1 levels and GH levels suppressible below 1 microg/l after an oral glucose load (75 g). Late potentials were not related to muscle mass index (127 +/- 35 active vs. 123 +/- 34 g/m2 cured/well controlled). The association of disease activity with the detection of late potentials was independent of age, gender, duration of the disease and body mass index. In comparison to the control group, the prevalence of late potentials was significantly higher in patients with acromegaly (23%) than in the control group (0%; P < 0.001).

CONCLUSIONS

Late potentials in the SAECG are frequently seen in active acromegaly and may represent an early and sensitive parameter to detect myocardial injury in acromegaly.

Long-term outcome in asymptomatic men with exercise-induced premature ventricular depolarizations

BACKGROUND

Exercise testing is widely used in the diagnosis of coronary artery disease, but the long-term outcome for asymptomatic persons with exercise-induced premature ventricular depolarizations remains unclear. We used data from the Paris Prospective Study I to assess the long-term outcome for such persons.

METHODS

A total of 6101 asymptomatic French men (42 to 53 years of age) who were free of clinically detectable cardiovascular disease underwent a standardized graded exercise test between 1967 and 1972. Subjects were prospectively classified as having or not having frequent premature ventricular depolarizations (a run of two or more consecutive premature ventricular depolarizations or premature ventricular depolarizations constituting more than 10 percent of all ventricular depolarizations during any of the 30-second electrocardiographic recordings).

RESULTS

During exercise, 138 subjects had frequent premature ventricular depolarizations. After 23 years of follow-up, these subjects had a higher risk of death from cardiovascular causes than the men without frequent premature ventricular depolarizations during exercise (relative risk, 2.67; 95 percent confidence interval, 1.76 to 4.07). In a multivariate model, with adjustment for age, body-mass index, heart rate at rest, systolic blood pressure, tobacco use, level of physical activity, presence or absence of diabetes, total cholesterol level, and the presence or absence of premature ventricular depolarizations before exercise and during recovery from exercise, both an exercise test that was positive for ischemia and the occurrence of frequent premature ventricular depolarizations during exercise remained independently associated with an increased risk of death from cardiovascular causes, with similar relative risks (2.63 [95 percent confidence interval, 1.93 to 3.59] and 2.53 [95 percent confidence interval, 1.65 to 3.88], respectively).

CONCLUSIONS

The occurrence of frequent premature ventricular depolarizations during exercise in asymptomatic middle-aged men is associated with a long-term increase in the risk of death from cardiovascular causes.