High-Precision Hemodynamic and Echocardiographic Assessment of Pacing in Obstructive Hypertrophic Cardiomyopathy

Area of Science:

• Cardiology
• Biomedical Engineering
• Hemodynamics

Background:

• Obstructive hypertrophic cardiomyopathy (oHCM) is characterized by left ventricular outflow obstruction, leading to significant symptoms and adverse outcomes.
• Right ventricular pacing (RVP) is a potential therapeutic strategy to desynchronize the left ventricle and alleviate this obstruction.
• However, RVP may also impair ventricular function, necessitating precise assessment of its effects.

Purpose of the Study:

• To precisely quantify the hemodynamic and echocardiographic effects of RVP in patients with oHCM.
• To determine the impact of varying atrioventricular delays (AVDs) on RVP efficacy.
• To assess the relationship between RVP, AVD, and cardiac output in oHCM.

Main Methods:

• Utilized high-precision assessment in 22 oHCM patients with dual-chamber pacing devices.
• Alternated between atrium-only pacing and AV-sequential RVP across a range of AVDs at different heart rates.
• Recorded continuous ECG, beat-by-beat outflow tract Doppler, and noninvasive blood pressure, fitting changes to parabolas for reproducible estimates.

Main Results:

• RVP at a mean heart rate of 75 bpm significantly reduced the left ventricular outflow tract gradient (LVOTg) by 8.31 mmHg at an optimal AVD of 173.2 ms.
• This optimal AVD also produced a mean peak systolic blood pressure increase of 2.47 mmHg.
• Higher heart rates (100 bpm) demonstrated greater systolic blood pressure increases and LVOTg reductions at hemodynamically optimal AVDs.

Conclusions:

• Multiple alternation assessment provides precise and reproducible quantification of RVP's hemodynamic and echocardiographic effects in oHCM.
• RVP can effectively reduce LVOTg while preserving or improving cardiac output.
• Atrioventricular delay (AVD) is a critical determinant of the hemodynamic response to RVP in oHCM.