MR-tomographic assessment of left ventricle biomechanics and elastic properties of ascending aorta in patients with extensive postinfarction aneurysm operated by the Dor method: retrospective analysis

Abstract

Introduction: Dor surgery is being improved and widely adopted in cardiac surgery as the most effective method for restoring the mechanical function of the left ventricle of the heart after massive myocardial infarction. However, the mechanisms for improving coronary blood flow, as well as the dynamics of aortic function, including its elasticity, have remained largely unstudied in prospective follow-up of patients with revascularization interventions on the coronary bed and simultaneous resection and plastic surgery of left ventricular aneurysms.

The purpose of the study was to examine changes in the biomechanics and pumping function of the left ventricular myocardium after the Dor procedure using contrast-enhanced MRI and to determine the characteristics of the elastic properties of the ascending aorta during the course of the Dor procedure, as well as to reveal their relationship with the improvement in myocardial condition as a result of this cardiac surgical intervention.

Material and methods: The Dor procedure was performed in 28 patients with extensive postinfarction left ventricular aneurysms. Pre- and post-operative cardiac MR tomographic examination was performed at rest, determining left ventricular myocardial mass, end-diastolic and end-systolic volumes, calculating the volume of damaged (fibrous) tissue following myocardial infarction, as well as left ventricular work per beat, aortic elastic distensibility, left atrium volume, and mitral valve regurgitation.

Results:  Preoperatively,  ventricular  end-diastolic  volume  was >200 ml in all patients, due to 30-40% transmural damage to the left ventricular muscle tissue, namely the aneurysm, which was further removed subtotally during the Dor procedure. As a result of the Dor operation, the left ventricle experienced a significant, more than 20 %, reduction in end-diastolic volume to 175-180 ml and a decrease in mass from 284 ± 17.9 g to 260 ± 17.6 g due to resection of the majority of the aneurysm. Contrast-enhanced MR imaging revealed a highly significant and substantial reduction in the proportion of myocardial damage, i.e., areas of left ventricular myocardial fibrosis, from 42 ± 7 % to 33.8 ± 10 %. The integrated indicator verifying the improvement in left ventricular biomechanics was associated to a highly significant and pronounced increase in the left ventricular ejection fraction, from a prognostically unfavorable 42 % to 48 % on average for the group indicating a significantly improved prognosis. Correlated with an enhancement in EFLV (r = 0.52, p < 0.05), an increase in the index of the ratio of LV work per beat to the end-diastolic volume (ALV/EDV) also unambiguously indicated a pronounced normalization of the Frank- Starling regulation of left ventricular contractility. The mitral valve annulus diameter significantly decreased after the Dor procedure from 31 ± 3.2 mm to 25 ± 2.8 mm (p < 0.05), although specialized prosthetic mitral rings were not implanted; this contributed to a decrease in the left atrial volume from 83.6 ± 23.9 ml to 68.1 ± 15.1 ml (p < 0.05). Systolic aortic distensibility, assessed as an increase in the ascending aorta volume during systole, also improved from 14.9 ± 5.56 ml to 21.1 ± 4.1 ml (p < 0.05).

Conclusion. The Dor procedure is a biomechanically rational and rightly effective intervention that improves left ventricular contractility and is accompanied by enhancements in aortic biomechanics, including meliorated systolic distension of the ascending aorta and subsequent diastolic advancing in coronary blood flow. Concurrently, the Dor surgery also improves left atrial hemodynamics associated with the mitral valve.