Improved coronary artery blood flow following the correction of systolic dyssynchrony with cardiac resynchronization therapy.
BACKGROUND
Coronary blood flow (CBF) is improved by cardiac resynchronization therapy (CRT) and impaired by right ventricular apical (RVA) pacing in patients with heart failure. However, the underlying mechanism remains unclear.


METHODS
Twenty-nine non-ischemic heart failure patients who responded to CRT underwent transthoracic echocardiography examination including both left anterior descending (LAD) CBF and tissue Doppler imaging in 3 pacing modes: intrinsic conduction, RVA pacing and biventricular (BiV) pacing. LAD velocity-temporal integral (LAD-VTI) and duration were measured. Systolic dyssynchrony was assessed with the standard deviation of a 12-left ventricular segmental model (Ts-SD).


RESULTS
BiV pacing improved while RVA pacing reduced CBF compared to intrinsic conduction (all p<0.05). Both Ts-SD and ventricular septal velocity deteriorated during RVA pacing but improved during BiV pacing (all p<0.05). When systolic dyssynchrony was induced, lower LAD-VTI (9.5 ± 3.4 versus 12.7 ± 5.1cm, p=0.001) and shorter LAD diastolic duration (483 ± 92 versus 542 ± 106 ms, p=0.010) were detected than synchronous status. Systolic dyssynchrony was inversely related to septal velocity (r=-0.41), p<0.001 and LAD-VTI (r=-0.30, p=0.007), with the latter found to be moderately correlated to septal velocity (r=0.30, p=0.007).


CONCLUSIONS
Regional LAD flow was improved in patients subjected to BiV but worsened in those treated with RVA pacing in non-ischemic heart failure CRT responders. Systolic dyssynchrony was more commonly observed in patients subjected to RVA pacing. Reduction of septal velocity with dyssynchrony may directly lead to reduced LAD flow. Improvement of septal velocity by CRT and hence LAD flow may be an important mechanism in determining the response to CRT.
Institute of Vascular Medicine, Li Ka Shing Institute of Health Sciences, SH Ho Cardiovascular Disease and Stroke Centre, Division of Cardiology, Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Fang
F
Fang
Joseph Yat-Sun
JY
Chan
Alex Pui-Wai
AP
Lee
Shih-Hsien
SH
Sung
Xiu-Xia
XX
Luo
Xin
X
Jiang
Joey S W
JS
Kwong
John E
JE
Sanderson
Cheuk-Man
CM
Yu
D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity / Q000502:physiology*; D058406:Cardiac Resynchronization Therapy / Q000639:trends*; D009202:Cardiomyopathies / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000628:therapy*; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013599:Systole / Q000502:physiology; D014463:Ultrasonography