Fasting glucose predicts heart rate recovery in CHD patients
MedWire News: Fasting plasma glucose (FPG) is an independent predictor of heart rate recovery (HRR) in people with coronary heart disease (CHD), research shows.
The findings suggest that the increased total and cardiovascular (CV) mortality associated with elevated FPG may be partly due to deleterious effects on autonomic CV regulation, as reflected by reduced HRR.
Postprandial glucose on the other hand is not a predictor of HRR.
As reported in the journal Diabetes & Metabolism, Anil Nigam (Montréal University, Quebec, Canada) and colleagues identified 4079 patients with FPG measurements and 706 with 2-hour postprandial glucose (2hPG) data from the Coronary Artery Surgery Study registry, a database of 24,958 patients with suspected or proven CHD, enrolled between 1974 and 1979.
The team examined the relationships between HRR and both FPG and 2hPG during a 14.7-year follow-up period.
They obtained the patients' vital status details through a mail-in survey completed between 1989 and 1991.
The authors found that increases in both FPG and 2hPG were significantly associated with decreased HRR.
In the FPG patients, those with impaired fasting glucose (IFG), defined by a FPG level of 100-125 mg/dl, had a lower mean HRR (46 bpm) than normoglycemic patients (49 bpm).
Similarly, in the 2hPG patients, those with postprandial hyperglycemia (PPH) in the nondiabetic range, defined by a 2hPG level of 140-199 mg/dl, also had a lower HRR (43 bpm) than those who were normoglycemic (47 bpm).
However, after adjusting for confounders (age, resting heart rate, maximum systolic blood pressure during exercise testing, and exercise tolerance), FPG remained an independent predictor of HRR, whereas 2hPG did not.
The study also showed that patients with IFG and those with higher FPG levels in the diabetic range both had higher resting heart rates than normoglycemic patients (75 and 77 vs 72 bpm, respectively), and lower maximum heart rates (137 and 133 vs 139 bpm) and heart rate reserves (63 and 67 vs 69%).
"This suggests not only reduced parasympathetic activity after maximum-intensity exercise, but additional abnormalities of autonomic function, including increased sympathetic nervous system activity at rest and/or limited activation of the sympathetic system during exercise," say the authors.
These two abnormalities of autonomic function have been linked to a higher risk of all cause and cardiovascular mortality including a greater risk of sudden death, they explain.
The lack of effect for 2hPG meanwhile "suggests less perturbation of autonomic regulation of CV function in patients with elevated postprandial glucose compared with those with raised FPG," write Nigam and team.
Further studies are required to determine whether or not treatment of raised FPG with lifestyle measures, including exercise, diet and weight loss, can restore autonomic function and lead to normalization of HRR, they conclude.
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By Sally Robertson