How His bundle pacing prevents and reverses heart failure induced by right ventricular pacing.

Ideal heart performance demands vigorous systolic contractions and rapid diastolic relaxation. These sequential events are precisely timed and interdependent and require the rapid synchronous electrical stimulation provided by the His-Purkinje system. Right ventricular (RV) pacing creates slow asynchronous electrical stimulation that disrupts the timing of the cardiac cycle and results in left ventricular (LV) mechanical asynchrony. Long-term mechanical asynchrony produces LV dysfunction, remodeling, and clinical heart failure. His bundle pacing preserves synchronous electrical and mechanical LV function, prevents or reverses RV pacemaker-induced remodeling, and reduces heart failure.

What Is the Heart? Anatomy, Function, Pathophysiology, and Misconceptions.

Cardiac dynamics are traditionally linked to a left ventricle, right ventricle, and septum morphology, a topography that differs from the heart's five-century-old anatomic description of containing a helix and circumferential wrap architectural configuration. Torrent Guasp's helical ventricular myocardial band (HVMB) defines this anatomy and its structure, and explains why the heart's six dynamic actions of narrowing, shortening, lengthening, widening, twisting, and uncoiling happen. The described structural findings will raise questions about deductions guiding "accepted cardiac mechanics", and their functional aspects will challenge and overturn them. These suppositions include the LV, RV, and septum description, timing of mitral valve opening, isovolumic relaxation period, reasons for torsion/twisting, untwisting, reasons for longitudinal and circumferential strain, echocardiographic sub segmentation, resynchronization, RV function dynamics, diastolic dysfunction's cause, and unrecognized septum impairment. Torrent Guasp's revolutionary contributions may alter future understanding of the diagnosis and treatment of cardiac disease.

Mitral regurgitation: anatomy is destiny.

Mitral regurgitation (MR) occurs when any of the valve and ventricular mitral apparatus components are disturbed. As MR progresses, left ventricular remodelling occurs, ultimately causing heart failure when the enlarging left ventricle (LV) loses its conical shape and becomes globular. Heart failure and lethal ventricular arrhythmias may develop if the left ventricular end-systolic volume index exceeds 55 ml/m2. These adverse changes persist despite satisfactory correction of the annular component of MR. Our goal was to describe this process and summarize evolving interventions that reduce the volume of the left ventricle and rebuild its elliptical shape. This 'valve/ventricle' approach addresses the spherical ventricular culprit and offsets the limits of treating MR by correcting only its annular component.

Effects of antegrade versus integrated blood cardioplegia on left ventricular function evaluated by echocardiographic real-time 3-dimensional speckle tracking.

OBJECTIVE: The objective of this study was to evaluate left ventricular free wall and interventricular septal function by 2-dimensional transthoracic echocardiography and live/real-time 3-dimensional transthoracic speckle tracking echocardiography before and after on-pump cardiac surgery and to assess the effect of mode of cardioplegia delivery. METHODS: A total of 22 patients were studied 1 day before and 4 to 5 days after surgery. Cold blood cardioplegia was delivered by intermittent antegrade infusion or by the integrated method. The latter includes a combination of intermittent antegrade and retrograde cardioplegia with a terminal warm amino acid-enriched reperfusion. RESULTS: The overall group displayed significant deterioration of septal function after surgery by 2-dimensional transthoracic echocardiography, as assessed by wall motion score index, yet subgroup analysis by 3-dimensional transthoracic speckle tracking echocardiography permitted distinction of outcomes achieved by antegrade or integrated delivery methods. Analysis after surgery showed that only the antegrade group displayed statistically significant deterioration in the strain parameters of some of the segments of the septum and free wall when strain was measured in the free wall and septum in the longitudinal, circumferential, and radial modes of deformation (P < .05). In contrast, only the integrated group displayed significant improvement in global radial, circumferential, and longitudinal strain (P < .05). CONCLUSIONS: These findings by 3-dimensional transthoracic speckle tracking echocardiography indicate that integrated cardioplegia offers superior myocardial protection of the left ventricular free wall and septum compared with the antegrade mode of cardioplegia delivery.

Ventricular structure-function relations in health and disease: part II. Clinical considerations.

Normal cardiac function of the left and right ventricles, together with the septum, is related to form/function interactions within the helical ventricular myocardial band. This knowledge is a prerequisite to understanding form/function interactions in diseases and for planning new treatments. Topics discussed include congestive heart failure in dilated hearts of ischaemic, valvar or nonischaemic origin as well as diastolic dysfunction. Similar thinking underlies novel treatments for dyssynchrony in pacing, together with focusing upon varying global left or right ventricular anatomy to correct mitral and tricuspid insufficiency caused by tethering of the leaflets. The septum is the lion of the right ventricle and insight is provided into offsetting septal damage during cardiac surgery, rebuilding its anatomical structure in post-tetralogy pulmonary insufficiency, as well as rectifying its dysfunction by decompression in patients with a left ventricular assist device.

Surgical ventricular restoration: where do we go from here?

The surgical treatment for ischemic heart failure (STICH) trial concluded that the addition of surgical ventricular restoration (SVR) to coronary bypass grafting did not lead to improved survival in patients with dilated ischemic cardiomyopathy. Observational studies at multiple centers over the last 15 years have shown consistent improvement in global ventricular function and approximately 70 % long-term survival. The causes of this discrepancy are reviewed here and likely relate to how the STICH trial was conducted. Recent subset analyses from the STICH investigators have provided some additional data relating ventricular volumes to outcomes. However, including patients with unsuitable entry criteria and operations confounds the data. We recommend an analysis of the STICH data based on the trial's initial design in order to determine if there are patients who may benefit by SVR.

Ventricular structure-function relations in health and disease: Part I. The normal heart.

The heart's structure-function relationships explain normal cardiac dynamics and clarify how they are disrupted by disease. For 500 years, anatomists described circumferential and helical cardiac fibres, yet disagreed about their relationships. One current model is attributed to Torrent Guasp who described functional pathways, the helical ventricular myocardial band (HVMB) with two interconnected loops: an outer basal loop with transverse fibres surrounds an inner apical helical loop that is composed of oblique descending and ascending segments that create a conical apical vortex. This review addresses the potential role of the HVMB in explaining the mechanics of isovolumic contraction, ejection, post-ejection isovolumic interval, rapid filling, torsion and recoiling. During the post-ejection isovolumic interval, a ∼ 90-ms hiatus exists between the end of contraction of the descending and the ascending segments. Compromise of this hiatus by disease disturbs the interdependence between torsion and 'untwisting' and impairs cardiac function. The validity of conventional expressions such as isovolumic relaxation, hyperechogenic septal line, untwisting and mitral valve opening will be revisited.