Elsevier

Heart Rhythm

Volume 8, Issue 1, January 2011, Pages 84-90
Heart Rhythm

Clinical
General
Improved heart rate recovery after marked weight loss induced by gastric bypass surgery: Two-year follow up in the Utah Obesity Study

https://doi.org/10.1016/j.hrthm.2010.10.023Get rights and content

Background

Obesity is associated with significantly increased cardiovascular mortality that has been attributed, in part, to sympathetic activation. Gastric bypass surgery (GBS) appears to increase long-term survival in the severely obese, but the mechanisms responsible for this increase are still being sought. Heart rate (HR) recovery after exercise reflects the balance of cardiac autonomic input from the sympathetic and parasympathetic systems. Blunted HR recovery is a very powerful predictor of increased mortality, whereas enhanced HR recovery portends a good prognosis.

Objective

The purpose of this study was to evaluate the effect of marked weight loss achieved via GBS on HR recovery.

Methods

Severely obese patients underwent submaximal exercise testing (80% predicted maximum HR) at baseline and 2 years after GBS (n = 153) or nonsurgical treatment (n = 188).

Results

Patients in the GBS group lost an average of 100 ± 37 lb compared to 3 ± 22 lb in the nonsurgical group (P <.001, GBS vs nonsurgical). Resting HR decreased from 73 bpm to 60 bpm in the GBS group and from 74 bpm to 68 bpm in nonsurgical patients (P <.001). HR recovery improved by 13 bpm in the GBS group but did not change in the nonsurgical group (P <.001 GBS vs nonsurgical). In multivariable analysis, the independent correlates of HR recovery at the 2-year time point were resting HR, treadmill time, age, body mass index, and HOMA-IR (an index of insulin resistance).

Conclusion

Marked weight loss 2 years after GBS resulted in a significant decrease in resting HR and an enhancement in HR recovery after exercise. These changes likely are attributable to improvement in insulin sensitivity and cardiac autonomic balance. Whether and to what extent this contributes to a reduction in cardiovascular mortality with GBS remains to be determined.

Introduction

Overweight and obesity are associated with increased overall mortality, particularly from cardiovascular disease.1, 2, 3, 4 Gastric bypass surgery (GBS) is becoming an increasingly popular weight loss method for many severely obese people.5 In addition to weight loss on the order of 40%,6 GBS patients generally see improvements in lipid profile,7 glucose tolerance,8 blood pressure (BP),9 endothelial function,10 and sleep apnea.11 A few studies have reported improvements in left ventricular function after GBS, although this is less well substantiated.12 The duration of the beneficial effects of GBS have not been fully established.13, 14 Although bariatric surgery is associated with potentially detrimental short- and long-term effects, the benefits appear to outweigh the risks. Recent data indicate significant reductions in total and cause-specific mortality in patients undergoing GBS.15 The mechanism(s) accounting for the decreased mortality is not fully known. Also unknown is whether there exist surrogate markers of survival that might help to more quickly evaluate outcomes associated with the expanding use of weight loss surgery.

The decrease in heart rate (HR) during the first 1 to 2 minutes after exercise termination, referred to as HR recovery, is an indirect measure of the balance between cardiac parasympathetic (vagal) and sympathetic tone.16, 17 Faster recovery of HR toward baseline is a marker of higher cardiovascular fitness levels, and in large studies more rapid HR recovery has been associated with better long-term survival.18 Conversely, reduced HR recovery is a strong indicator of high cardiovascular risk and higher mortality.18, 19 It has recently been reported that a short-term (12 week), diet-based weight loss program in overweight men resulted in a significant increase in HR recovery after maximal exercise.20 However, whether similar benefits can be attributed to weight loss induced by GBS and the duration of such benefits are unknown.

In the current study, we measured HR recovery after exercise at baseline and 2 years after GBS or nonsurgical treatment. We hypothesized that marked weight loss after GBS would be associated with improvement in HR recovery.

Section snippets

Study population

The study protocol was approved by the institutional review board of the University of Utah Health Sciences Center. All patients signed a written consent form. The rationale and design of the Utah Obesity Study has previously been reported.21 From among the 1,156 initial patients, we studied 341 patients (GBS group, n = 153; nonsurgical group, n = 188) who had complete treadmill data at both baseline and 2-year follow up. Roux-en-Y GBS was performed in all surgical patients. The procedure was

Patient characteristics

The population was 85% female in the GBS group and 81% female in the nonsurgical group. Age at the beginning of the study was 43 ± 11 years in the GBS group and 48 ± 11 years in the nonsurgical group. Subjects in the GBS group lost an average of 100 ± 37 lb (range 0–263 lb). The nonsurgical group lost an average of 3 ± 22 lb (range +52 to –130 lb). Anthropomorphic and blood chemistry variables all improved with significant weight loss in the GBS group (Table 1).

Discussion

Our data show that significant weight loss 2 years after GBS is associated with (1) markedly improved exercise capacity, (2) a reduction in resting HR and systolic BP, and (3) a marked improvement in HR recovery after exercise. These changes are likely contributed to by a relative enhancement of cardiac vagal tone, with potential contributions from decreased resting sympathetic tone and more rapid sympathetic withdrawal after termination of exercise. The improvements in the physiologic

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    This investigation was supported by National Institutes of Health (NIDDK) Grant DK-55006, National Institutes of Health Grant R01 HL084294-01 A1, and Public Health Service Research Grant No. M01-RR00064 from the National Center for Research Resources.

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