Late ventricular structure after partial left ventriculectomy

Models versus established knowledge in describing the functional morphology of the ventricular myocardium

The myocytes comprising the ventricular mass are arranged so as to function in antagonistic fashion, the walls having the capacity to generate both constrictive and dilatory forces. This dualistic activity is organized on the basis of a site-specific morphologic pattern, permitting marked regional specificity for mural motion and providing a target for regional therapy. Diseased regions can be removed surgically without danger of jeopardizing the remaining healthy mural segments. The sensitivity of the intruding population of myocytes to positive and negative inotropic medication is markedly more pronounced than that of the prevailing tangentially aligned myocytes. This asymmetrical action of inotropes in the setting of global ventricular imbalance promotes the potential to restore constrictive as opposed to dilatory actions.

The relationship between structure and function: why does reshaping the left ventricle surgically not always result in functional improvement?

Surgical strategies recently introduced to improve ventricular function have been based on the concepts of reduction of ventricular diameter, synchronization of myocardial activity, passive support of diastolic ventricular shape, and active support of systolic ventricular constriction. They have depended on several established theoretical assumptions, not all of which are totally valid. Clinical results have proved markedly variable. This is especially true for procedures designed to reduce the radius of the left ventricle. Some have reported up to 80% mortality, whereas others achieve results comparable with those for heart transplantation. Because of this, the method runs the risk to be rejected, or else, its more widespread application will be postponed until essential details concerning the basic concepts have been elucidated. It is these details which we discuss in this review.

A critical evaluation of results of partial left ventriculectomy

BACKGROUND

Because of the variation in the surgical procedures designed to reduce ventricular radius, along with differences in hospital care, it is difficult to disentangle the factors that may contribute to the success or failure of the partial left ventriculectomy.

METHODS AND RESULTS

We undertook partial left ventriculectomy in 18 patients, 10 suffering from idiopathic dilated cardiomyopathy and 8 from ischemic heart disease. We assessed the amount of reduction in wall stress, the systolic thickening of the ventricular wall, and the extent of connective tissue in the excised segment of the wall. Of the overall group, six patients died, three from infarction, one of stroke, one with asystole, and one with ventricular fibrillation. The mean decrease in measured mesh tension was 40% (p < 0.001). Most patients exhibited improvements postoperatively in terms of the systolic thickening of the posterior and superior free walls of the left ventricle. In those in whom the events could be monitored, life-threatening arrhythmias posed complications in three of four patients with ischemic heart disease, and in two of six patients suffering from idiopathic dilated cardiomyopathy. In one patient, death was associated with a transmural alignment of fibrous tissue.

CONCLUSIONS

Our measured reductions in myocardial mesh tension were in keeping with the anticipated theoretical reduction in wall stress expected from partial ventriculectomy. The basic concept underscoring surgical maneuvers to reduce ventricular radius, therefore, is sound. A potential trap is the resection of the marginal artery. Critical myofibrosis was a rare complication. Arrhythmias, which are common, can successfully be treated by implantation of antitachycardic and defibrillatory devices.

The structure and function of the helical heart and its buttress wrapping. VI. Geometric concepts of heart failure and use for structural correction

The macroscopic basis for congestive heart failure is defined as conversion of a helical heart, whereby the apical loop fiber angle orientation that produces a 60% ejection fraction becomes more transverse to develop a spheric configuration. The geometric consequence is flattening of the apical loop architecture, so that the 15% shortening can produce only 30% ejection fraction. The fundamental shape change is alteration of normal relationships between the transverse basal loop and oblique apical loop, to make the apical loop become more basal through more transverse fiber orientation. These fundamental architectural changes are then used to evolve new procedures that restore a more normal, helical, ventricular architecture in ischemic and dilated cardiomyopathy. Direct intraoperative ventricular methods underlie surgical ventricular restoration or endoventricular surgical patch plasty procedures, the Batista procedure, and Pacopexy. These intraventricular objectives are then compared with external approaches without ventriculotomy (ie, reimplantation of cells, pericardial sleeve (acorn), surface radiofrequency ablation, and the myocor approaches). A survey of current direct ventricular clinical results that improve the underlying nondamaged muscle (ie, remote segment) is defined, and related to timing of procedures directed at rebuilding more normal ventricular shape before irreversible collagen and fibrosis develop. The overall intent is to convert the spheric heart into an elliptic configuration. Novel concepts are introduced to suggest an internal ventricular patch can be used as an intercavitary curtain, through covering nonscarred septal muscle (ie, normal but distended) to amplify left ventricular function through producing a more helical structure.