Cardiovascular Implantable Electronic Devices -> Bradycardia Devices: -> Indications D-PO02 - Poster Session II (ID 47) Poster

D-PO02-112 - Automated, High-precision Echocardiographic And Haemodynamic Assessment Of Atrioventricular Interval During Right Ventricular Pacing For Hypertrophic Obstructive Cardiomyopathy (ID 1521)


Background: The role of right ventricular pacing (RVP) in reducing left ventricular outflow tract (LVOT) obstruction in hypertrophic obstructed cardiomyopathy (HOCM) remains controversial.
Objective: To identify the optimal AVI using automated, high-precision haemodynamic and echocardiographic measurements.
Methods: 12 patients with HOCM and pacemakers in situ were recruited. Pacing mode was alternated between atrial pacing (AAI) and AV sequential RVP (DDD) 10 times whilst recording continuous beat-by-beat blood pressure (BP) and continuous wave doppler through the left ventricular outflow tract (LVOT-CWD). This was repeated for a full range of AVIs. Automated software detected the trough of the LVOT-CWD trace to identify beat-by-beat instantaneous gradient (LVOTg). The change in LVOTg was the mean difference when transitioning pacing mode between AAI and DDD. Automated analysis of beat-by-beat BP was similarly performed. Averaging beat-by-beat BP and LVOTg across pacing transitions accounts for physiological drift and automation reduces bias.
Results: Mean LVOTg was 37 ± 19 mmHg. At 10 bpm above sinus rate, optimal AVI reduced LVOTg (-14.2 ± 5.3 mmHg, p<0.05) without reducing BP (0.5 ± 0.7 mmHg, p=0.39). Individual data revealed an AVI where LVOTg was reduced and BP preserved in 10 patients (median AVI 160). Compared with 10 bpm above sinus rate, at 100 bpm greater LVOTg reduction was seen (-23.4 ± 6.54 mmHg, p<0.05) and BP appeared improved (7.0 ± 3.7 mmHg, p=0.07) rather than merely preserved.
Conclusion: High precision automated measurements detect the AVI that balances the increased LVOT size, reduced myocardial performance and altered AV filling that occur with RVP for HOCM.