Coronary artery bypass grafting is associated with a significant worsening of QT dynamicity and heart rate variability.
BACKGROUND
Imbalance in autonomic nervous system and impaired myocardial repolarization has been shown to increase the risk for arrhythmias in patients with coronary artery disease. This study evaluated the effects of coronary artery bypass grafting (CABG) on heart rate variability and QT interval dynamicity in subjects with coronary artery disease undergoing elective CABG surgery.


METHODS
The study group consisted of 68 consecutive patients (mean age +/-SD: 61 +/- 9 years) with coronary artery disease who underwent elective CABG. Twenty-four-hour Holter monitoring was performed 2-5 days before cardiac surgery and was repeated 10 days after CABG. ELATEC holter software was used to calculate heart rate variability and QT dynamicity parameters. All subjects had a complete history, laboratory examination and transthoracic echocardiography.


RESULTS
All patients had beta-blocking agent medication pre- and postoperatively. Standard deviation of all NN intervals for a selected time period, square root of the mean of the sum of the squares of differences between adjacent RR intervals, the proportion of differences in successive NN intervals greater than 50 ms, normalized low-frequency power, and normalized high-frequency power were significantly decreased after CABG surgery, whereas low-frequency/high-frequency ratio was significantly increased after CABG. QT/RR slopes over 24 h were significantly increased after CABG surgery for QT end and QT apex (QTapex/RR: 0.16 +/- 0.13 vs. 0.28 +/- 0.19, p < 0.001; QTend/RR: 0.18 +/- 0.13 vs. 0.36 +/- 0.23, p < 0.001).


CONCLUSIONS
This prospective study showed for the first time that CABG was associated with a significant worsening of heart rate variability and QT dynamicity parameters in the postoperative period.
Yavuz
Bunyamin
B
Department of Cardiology, Hacettepe University Faculty of Medicine, Ankara, Turkey. bunyamin@hacettepe.edu.tr
Duman
Umit
U
Abali
Gulcan
G
Dogan
Omer Faruk
OF
Yazicioglu
Alkin
A
Sahiner
Levent
L
Aytemir
Kudret
K
Tokgozoglu
Lale
L
Demircin
Metin
M
Nazli
Nasih
N
Kabakci
Giray
G
Oto
Ali
A
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D003327:Coronary Disease / Q000503:physiopathology* / Q000601:surgery; D017558:Elective Surgical Procedures; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology
D000319:Adrenergic beta-Antagonists