Inter-Basal and Septal Connections of Papillary Muscles - An Anatomical Rationale for Rhythmic Opening of AV Valves - A Multicentric Medical College Based Cross Sectional Study

BACKGROUND The papillary muscle basal connections have significant clinical implications. Variety of studies done on its morphology and function by various specialists in different departments. A close look on these revealed the interconnections of papillary muscles to one another and to the interventricular septum of both ventricles is related to uncoordinated contractions of papillary muscles, leading to hyper or hypokinesia or prolapse or even its rupture. METHODS Our study done in 25 formalin soaked hearts revealed after the deep and meticulous dissection, reflecting the walls of ventricles laterally the numerous interconnections of papillary muscles at its bases and IVS. Ventricles are opened by inverted ‘L’ shaped incision and its reflected more laterally till all the papillary muscles is visible in one frame after incising the moderator band. The connections were noted, measured, photographed, tabulated, compared with similar studies and analysed with experts with respective fields. RESULTS Almost all the specimens did have the interconnections. Further the post mortem findings of the cardiac related deaths with involvement of papillary muscles suggest damage to such ‘bridges’. The moderator band extensions to the base of right APM, and its extension to the posterior groups is noted in all the specimens. The bridge from the IVS to bases of both the groups of papillary muscles is noted in left ventricle. In90% of specimens the one PPM is found to be loosely connected, more so in left ventricle. CONCLUSIONS We are of a conclusion that such basal interconnections and to the interventricular septum are responsible for rhythmic contractions of papillary muscles of both ventricles. Since the AV valves have to open simultaneously, interconnections becomes mandatory as the impulse has to reach it before it reaches the trabeculae carniae. One of the Posterior papillary muscles is loosely connected to other papillary muscles, may be the reason for its rupture, more so in left ventricle. KEYWORDS Papillary Muscle, Interbasal Connection, Moderator Band, Valvular Prolapse, AV Valves

Proarrhythmic Effect of RF ablation on the Right Ventricular Moderator Band

The right ventricular moderator band (MB) is increasingly being recognized as a source for PVCs and PVC-mediated ventricular fibrillation. Monomorphic PVCs, non-sustained monomorphic VT and ventricular fibrillation are all documented arrhythmias originating from the MB. The benign PVCs usually have a coupling interval in excess of 400 msec. When PVCs trigger VF, coupling intervals are typically short, less than 300 msec. We report here a case of long-standing frequent monomorphic PVCs with a coupling interval of > 400 msec from the right ventricular distal conduction system embedded in the moderator band that progressed to non-sustained ventricular tachycardia. Following suppression of the arrhythmia with RF ablation, the arrhythmia recurred with PVCs at a shorter coupling interval (<300 msec), with frequent repetitive non-sustained polymorphic VT and triggering of sustained ventricular fibrillation. The use of a cryoballoon to ablate over the course of the moderator band resulted in complete and durable suppression of ventricular arrhythmias.

Novel Speckle Tracking Analysis Showed Excellent Reproducibility for Size and Shape of the Fetal Heart and Good Reproducibility for Strain and Fractional Shortening

<b><i>Introduction:</i></b> This study aimed to evaluate reproducibility and agreement of fetal cardiac shape and deformation using <i>FetalHQ</i>. <b><i>Methods:</i></b> Fifty normal fetuses at 20–38 weeks of gestation were evaluated. Two operators independently selected an optimal cardiac cycle using <i>FetalHQ</i>^®™software for speckle tracking analysis. Intra- and interobserver correlation coefficient and limits of agreement for cardiac shape and deformation were estimated. <b><i>Results:</i></b> Global cardiac markers: high correlation (<i>r</i> = 0.98) and agreement (mean difference, standard deviation [MD, SD] 5.07, 75.8) for ventricular area; moderate correlation (<i>r</i> = 0.78) and agreement (MD, SD: 0.016, 0.08) for global sphericity index (SI) and for left ventricle (LV) global strain (<i>r</i> = 0.65; MD, SD: −4.48, 11.9); and low but still significant correlation (<i>r</i> = 0.58) and agreement (MD, SD: −3.77, 12.27) for right ventricle (RV) global strain. For individual ventricular parameters: high correlation for LV ([median <i>r</i>; range] 0.98; 0.93–0.99) and RV (<i>r</i> = 0.98; 0.97–1.0) SI, and for LV (<i>r</i> = 0.92: 0.56–0.99) and RV (<i>r</i> = 0.96; 0.67–0.99) end diastolic diameters; moderate correlation for LV fractional shortening (<i>r</i> = 0.53; 0.87–0.98); and no significant correlation for RV fractional shortening (<i>r</i> = 0.36; 0.32–0.97). Inter- and intraobserver correlation and agreement were similar for all evaluated parameters. <b><i>Conclusion:</i></b> Speckle tracking analysis of the fetal heart provides reliable estimations of global and LV shape and deformation. Low correlation in the RV can be related to anatomical structures such as the moderator band.

Arrhythmias from the Right Ventricular Moderator Band: Diagnosis and Management

The moderator band in the right ventricle is being increasingly recognised as a source for arrhythmias in the absence of identifiable structural heart disease. Because it carries part of the conduction system from the right ventricle septum to the free wall, it is a source of Purkinje-mediated ventricular arrhythmias that manifest as premature ventricular contractions (PVC) or repetitive ventricular tachycardia. More importantly, short coupled PVCs triggering polymorphic ventricular tachycardia and VF have been localised to the moderator band and ablation of these Purkinje mediated PVCs can effectively prevent recurrent VF. The exact mechanism of arrhythmogenesis is still debated but stretch, fibrosis and ion channel alterations might be responsible. Arrhythmias originating in this region of the right ventricle may thus be another cause for idiopathic VF that is potentially treatable with catheter-based ablation techniques. Recognition of the typical PVC morphology can point to the moderator band as the source of idiopathic VF and an opportunity for timely intervention. The available data on the anatomy, electrophysiology and management options are reviewed.