787 Ablation of the ventricular ectopic foci: a therapeutic option for dilated cardiomyopathy due to arrhythmic MVP

Aims A subset of patients with mitral valve prolapse (MVP) are affected by a still not well understood condition characterized by frequent ventricular arrhythmias (mostly originating from papillary muscles) and sudden cardiac death (SCD). It is called MVP malignant syndrome (MVP MS). In these patients, the high arrhythmic burden may lead to left ventricular (LV) dyssynchrony and dysfunction, determining a tachycardia-induced cardiomyopathy (TIC). Reduction in arrhythmic burden determines LV recovery and ejection fraction improvement and interrupts LV progressive dilatation. Methods and reports We report the case of a 52-year-old woman with MVP and family history of both MVP and SCD who was referred to our department for symptomatic extrasystoles and dyspnoea during exercise. Palpitations begun 11 years before: in that occasion she performed a 3-lead-ECG-Holter monitoring which documented 3457 ventricular extrasystoles. Transthoracic echocardiography (TTE) showed normal LV dimension and function and a myxomatous mitral valve with prolapse of both leaflets. At that time beta-blocker therapy was introduced, but soon suspended because of patient’s clinical intolerance (bradycardia and hypotension). Since then she was lost at follow-up for years, until symptoms worsened. When she came to our attention, TTE showed dilated and hypokinetic LV (ejection fraction was 38%, S2 wave at TDI was 6.4 cm/s and global longitudinal strain value was −13%). CMR was performed and confirmed TTE findings. Mitral-annulus disjunction was described in anterior, lateral, and posterior wall and late gadolinium enhancement analyses showed subendocardial fibrosis in correspondence of the posterior papillary muscle (PM) and in the mid-inferior wall. Holter monitoring enlightened a high arrhythmic burden with 24 065 premature ventricular complexes (PVCs) of two morphologies (right bundle branch block-like and −120° axis and right bundle branch block-like and −75° axis). During stress test, PVCs increased as the heart rate increased, resulting in bigeminism at peak exercise. Considering all these features, we hypothesized a case of MVP MS in which the high ventricular arrhythmic burden resulted in TIC. Any available pharmacological attempt to reduce arrhythmias failed. Transcatheter (TC) ablation of PVCs was then proposed. Electrophysiological study identified the inner part of the posterior papillary muscle implantation region and the antero-lateral basal wall as PVCs sites of origin. Radiofrequency ablation was performed in both sites. After the procedure, despite an incomplete suppression of the posterior PM focus, 12-lead 24-h Holter monitoring and TTE performed during the hospitalization showed a consistent arrhythmic burden reduction and LV function improvement. At 6 months from the procedure, symptoms improved and Holter monitoring showed 7515 PVCs with a 54% arrhythmic burden reduction compared with the presentation. TE showed lower LV end-diastolic volume and an increase in ejection fraction up to 47%; global longitudinal strain was −17% and TDI showed a S2 wave on lateral wall of 11 cm/s, confirming left ventricle improvement after the arrhythmic burden reduction. Conclusions Complete suppression of PMs PVCs with TC ablation is difficult to obtain, especially when the focus is in the inner part of the PM and TC ablation of ventricular arrhythmias in MVP patients has not yet demonstrated his efficacy in reducing SCD. Nevertheless, it should be taken into consideration to obtain at least PVCs reduction in patients with high arrhythmic burden leading to TIC.

Characterization of Spontaneous Vascular Findings in the Papillary Muscles of Beagle Dogs

Standard histology trimming practices for toxicity studies in dogs include preparation of a section of the papillary muscle associated with the left ventricular free wall—the anteriolateral or anterior muscle. In contrast, the posteromedial or posterior papillary muscle, associated with the interventricular septum, is not commonly evaluated. In humans, the posterior papillary muscle is more often affected in ischemic myocardial disease, in large part due to the absence of collateral circulation, in contrast to the anterior muscle. Due to the differential vascular supply to the papillary muscles, we sought to determine whether there is a higher incidence of spontaneous coronary vascular changes in the posterior papillary muscle versus the anterior muscle in dogs. The hearts of 30 vehicle-treated or untreated beagle dogs that were euthanized for other purposes were collected and sectioned in a consistent manner to include both papillary muscles for histologic evaluation. The posterior muscle consistently had higher incidences of intramural coronary arteries affected by vascular medial hypertrophy, medial arteriosclerosis, intimal hyperplasia, and/or disruption or loss of the internal elastic lamina. This observation may have significant implications for the evaluation and characterization of spontaneous and xenobiotic-induced cardiovascular lesions in dogs.

Morphological features of papillary muscles in the right ventricle

Our study was performed by dissecting formalinized cord, aiming at:the number of bodies of each papillary muscle in the right ventricle, the shape of the muscular body, also the morphological characteristics of the tendon chordaes. The anterior papillary muscles of the right ventricle, were studied on 54 cords, finding a total of 82 papillary muscles. Unique anterior papillary was found in 59.26% of case, representing 38.10% of total anterior papillary muscles. In 29.63% of cases, the anterior papillary muscle was double and in 11.11% of cases was threefold. The conical shape we found in 57.32% of the anterior papillary muscles, and the cylindrical shape encountered in 29.27% of cases. In case of double papilaery muscles, sometimes beeing joined at various levels between them, they realized particular aspects in each 2.44 % of cases, presenting the „N” and „H” letter appearance and in 1.22% of cases one of the two papilary presented an arcuate shape. At the unique papillary in one case (1.22%) we have found pyramidal forms and reversed „V” letter. The valvular tendinous chordae of the anterior papillaries, we have pursued on a number of 78 papillary muscles and we found that most frequently they broke loose from the superior side, in 41.03% of cases detaching from the tip of conical unique papillaries romthe superior si of those cylindrical. The posterior papillar muscles of the rght ventricle we studied on 42 cords, presenting 69 papillary muscles. Single posterior papillary muscle we found in 52.38% of cases, in 33.33% of cases was double, triple in 11.90% of cases and in one case (2.38%) the posterior papillry was quadruple. Most commonly, the posterior papillary muscle presents a conical shape, aspect found in 65.22% of cases, in 27.54% of cases was cylindric, in 2.90% of cases we found a papillary muscle in reversed „Y” shape (at double papillary), and in one single case (1.54%) we found one arcuated papillary (in one double paillary), one irregular papillary (at unique papillaries) and one papillary in reversed „N” letter (between two muscular bodies of one triple papillary). Valvular chordaes of the posterior papillary muscles, most frequently broke loose from the tip or superior edge of the papillary, aspect found in 35.48% of cases. Septal papillary muscles that we studied on 43 cords, were represented either by a number of 3-5 beams, or 5-9 simpe chordae tendons, both tipes could present or not at their origin on the septomarginal strip, a muscular cone. Rarely can present 1-3 large muscular cones that sometimes can be considered true papillary muscles. We found the arterial muscle cone, present in all cases, beeing represented by chordae bundles arising from a muscular cone and rarely not showing muscular cone at his origin or can be represented by two beams of valvular chordae. We encountered one case where septal papillaries were represented by 3 conical muscular bodies, well represented, comparable in size with the anterior and posterior papillary muscles, especially the superior and inferior muscular bodies, the middle beeing shorter. We found in 13.95% of cases the existence of the posterior’s angle papillary muscle of the right ventricle, conical and cylindrical papillary muscle, that sent tendon chordae only to the septal leaflet.

Anatomical consideration of the number and form of the papillary muscle in the left ventricle

Our results were obtained by dissection of 56 cords, wich presented at the papillary muscle of the left ventricle, 106 muscular bodies and from those, 58 muscular bodies were for the anterior papillary muscle and 48 for the posterior papillary muscle. Anterior papillary muscle was studied on 32 cords, and the posterior papllary muscle on 24 cases. Of the 106 papillary muscles we analized, unique papillary muscle was incountered in 16 cases, 10 being at the anterior papillary muscle and 6 cases at the posterior papillary muscle.. The papillary muscle formed of two muscular bodies (double) presented a number of 64 muscular bodies, 36 being at the anterior papillary and 28 at the posterior papillary. In cases of triple papillary muscle, from 18 muscular bodies, 12 were from the anterior papillary and 6 were from posterior papillary. In the two cases of quadruple papillary muscle the 8 muscular bodies belonged to the posterior papillary muscle. Amoung the total muscular bodies, most frequently they had a conical hape, aspect found in 67 cases, 33 cases being seen in the anterior papillary muscle and 34 in the posterior papillary. In 20 cases the muscular bodies were cylindrical, 18 cases were found in the anterior papillary and 2 in the posterior papillary muscle. In 10 cases the muscular bodies were arcuated, 4 cases being to anterior papillary and 6 cases to the posterior papillary muscle. In 8 cases the bodies were fusiform, 4 cases being to the anterior papillary and 4 to the posterior papillary muscle. In one case to an unique posterior papillary muscle we found a particullar form of the muscular body, wich we called „the torch“ or the „beacon“ that have the muscular body thinner at the lower half and the size increasing in width, reaching a maximum width at its upper extremity, from where are detaching four extra muscles that gave birth to beams of valvular chordage. In case of papillary muscles with two muscular bodies, they can sometimes be linked by a muscular bridge, transverse or oblique, making characteristical features. Thus, in 6 cases, the muscular bridges realized the H“ letter appearance, 4 cases being at the anterior papillary muscle and 2 at the posterior papillary. In 4 cases only at the anterior papillary the bridges formed „N“ letter aspect, 2 cases were at the anterior papilllary and 2 in the posterior papillary muscle. Also in 4 cases, the presence of the bridges acheve the appearance of reversed „N“ letter, 2 cases were in the anterior papillary and 2 in the postertior papillary.