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[Atrial synchronous ventricular stimulation with reduced a.v. delay time as a therapeutic principle in hypertrophic
Insights
Transitory electrostimulation can reduce left-ventricular pressure gradients in hypertrophic obstructive cardiomyopathy (HOCM). This diagnostic pacing, particularly with prematurity between 5-20 ms, offers a potential therapeutic principle for HOCM patients.
Area of Science:
- Cardiology
- Electrophysiology
Context:
- Hypertrophic obstructive cardiomyopathy (HOCM) presents a significant left-ventricular pressure gradient at rest.
- Currently, causal therapies for HOCM with a resting pressure gradient are limited.
- Previous observations suggested that premature ventricular excitation could reduce this gradient.
Purpose:
- To investigate the therapeutic potential of temporary electrostimulation from the right ventricular apex in reducing left-ventricular pressure gradients in HOCM patients.
- To determine the optimal prematurity settings for achieving maximum gradient reduction.
Summary:
- Twenty-three HOCM patients with a resting gradient ≥30 mm Hg underwent VOO, VAT, and DOO pacing with varying atrio-ventricular delays.
- Significant gradient reductions (≥51%) were observed in 5 patients (Group A), moderate reductions (30-50%) in 12 (Group B), and minor reductions (<29%) in 6 (Group C).
- Optimal gradient reduction was achieved with prematurity between 5-20 ms, not associated with decreased stroke volume but improved outlet opening.
Impact:
- Temporary diagnostic pacing can induce a modified excitation pattern, decreasing functional obstruction in a subset of HOCM patients.
- This approach offers a therapeutically relevant partial success by mitigating systolic function disturbances.
- The study recommends temporary diagnostic pacing for HOCM patients with significant resting gradients and outlines prerequisites for permanent electrostimulation.
Abstract:
For the hypertrophic obstructive cardiomyopathy with left-ventricular pressure gradient in rest a causal therapy is nowadays not yet known. Therefore, it should be tested, in what respect from former observations over reductions of the pressure gradient by an untimely foreign excitation of the ventricles from the apex of the right ventricle a therapy principle can be derived. For this purpose out of a group of 84 patients by left-right heart catheterization, coronarography, computer cardio-tomography and scintigraphy of the myocardium 23 test persons with typical hypertrophic obstructive cardiomyopathy and a left-ventricular gradient in rest greater than or equal to 30 mm Hg were selected for the transitory electrostimulation. After placing of one electrode in the right atrium and another one in the right ventricle one after another a VOO-, VAT- and DOO-pacing were used. For the two last mentioned forms of stimulation as electronic atrio-ventricular retardation times 100, 40, 20, 10 and 5 ms were selected. With all three kinds of stimulation in 5 of the patients (group A) reductions of gradients greater than or equal to 51% and in 12 cases of hypertrophic obstructive cardiomyopathy (group B) diminishments between 30 and 50% could be obtained. Only in 6 patients (group C) reductions of less than or equal to 29% were registered. The optimum of prematurity necessary for obtaining maximum pressure reductions is individually different, but is almost in every case between 5 and 20 ms. Further seven parameters measured during the stimulation phases showed that these reductions are not caused by a decrease of the stroke volume, but by an enlargement of the effective opening of the outlet. Apparently, in a part of the patients with hypertrophic obstructive cardiomyopathy by the foreign excitation from the apex of the ventricle a temporary and spatial course of excitation can be induced, by means of which the degree of functional stenosing is decreased. Since for several patients the removal of the disturbance of the systolic function is to be regarded as therapeutically reasonable partial success, the transitory diagnostic pacing is recommended for all patients with typical hypertrophic obstructive cardiomyopathy and a gradient in rest greater than or equal to 30 mm Hg. The indications and technical prerequisites for a permanent electrostimulation with suitable systems are represented.