Cardiac resynchronization therapy upregulates cardiac autonomic control.
OBJECTIVE
To determine the effect of cardiac resynchronization therapy (CRT) on sympathetic nervous function in heart failure (HF).


BACKGROUND
Neurohormonal dysregulation and cardiac autonomic dysfunction are associated with HF and contribute to HF progression and its poor prognosis. We hypothesized that mechanical resynchronization improves cardiac sympathetic function in HF.


METHODS
Sixteen consecutive patients receiving CRT for advanced cardiomyopathy and 10 controls were included in this prospective study. NYHA class, 6-minute walk distance, echocardiographic parameters, plasma norepinephrine (NE) were assessed at baseline, 3-month and 6-month follow-up. Cardiac sympathetic function was determined by (123)iodine metaiodobenzylguanidine ((123)I-MIBG) scintigraphy and 24-hour ambulatory electrocardiography.


RESULTS
Along with improvement in NYHA class (3.1 +/- 0.3 to 2.1 +/- 0.4, P < 0.001) and LVEF (23 +/- 6% to 33 +/- 12%, P < 0.001), delayed heart/mediastinum (H/M) (123)I-MIBG ratio increased significantly (1.8 +/- 0.7 to 2.1 +/- 0.6, P = 0.04) while the H/M (123)I-MIBG washout rate decreased significantly (54 +/- 25% to 34 +/- 24%, P = 0.01) from baseline to 6-month follow-up. The heart rate variability (HRV) measured in SD of normal-to-normal intervals also increased significantly from baseline (82 +/- 30 ms) to follow-up (111 +/- 32 ms, P = 0.04). The improvement in NYHA after CRT was significantly associated with baseline (123)I-MIBG H/M washout rate (r = 0.65, P = 0.03). The improvement in LVESV index was associated with baseline (123)I-MIBG delayed H/M ratio (r =-0.67, P = 0.02) and H/M washout rate (r = 0.65, P = 0.03).


CONCLUSIONS
After CRT, improvements in cardiac symptoms and LV function were accompanied by rebalanced cardiac autonomic control as measured by (123)I-MIBG and HRV.
Cha
Yong-Mei
YM
Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. cha.yongmei@mayo.edu
Oh
Jae
J
Miyazaki
Chinami
C
Hayes
David L
DL
Rea
Robert F
RF
Shen
Win-Kuang
WK
Asirvatham
Samuel J
SJ
Kemp
Brad J
BJ
Hodge
David O
DO
Chen
Peng-Sheng
PS
Chareonthaitawee
Panithaya
P
D019797:3-Iodobenzylguanidine; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology*; D017147:Defibrillators, Implantable; D015716:Electrocardiography, Ambulatory; D005246:Feedback; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology* / Q000517:prevention & control*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood*; D019275:Radiopharmaceuticals; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000503:physiopathology* / Q000517:prevention & control*
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine; D009638:Norepinephrine