Thursday, December 6, 2012

Impact of Reduced Heart Rate Variability on Risk for Cardiac Events

A decreased heart rate variability was found to be associated with increased cardiac events in this study.

Impact of Reduced Heart Rate Variability on Risk for Cardiac Events

Thursday, November 29, 2012

Detection of left anterior descending coronary artery stenosis in patients with left bundle branch block: exercise, adenosine or dobutamine imaging

This study found the exercise stress combined with myocardial perfusion imaging in people with LBBB is more sensitive that vasodilator stress in the prediction of stenosis on angiography, although this difference did not reach statistical significance.

ScienceDirect.com - Journal of the American College of Cardiology - Detection of left anterior descending coronary artery stenosis in patients with left bundle branch block: exercise, adenosine or dobutamine imaging?

Coronary artery surgery study (CASS): a randomized trial of coronary artery bypass surgery. Survival data.

Is bypass surgery better than medical therapy for patients with stable ischemic heart disease? What about patients with triple vessel disease? This landmark study found that the mortality rate was no different in those undergoing bypass surgery compared to those undergoing medical therapy, even those with triple vessel disease.

Coronary artery surgery study (CASS): a randomized trial of coronary artery bypass surgery. Survival data.

Wednesday, September 19, 2012

The heart rate response to adenosine: A simple predictor of adverse cardiac outcomes

BACKGROUND: the normal response to adenosine infusion typically is an increase in the heart rate of 20% or more to compensate for adenosine induced vasodilation.

METHODS: this study looked at asymptomatic diabetics undergoing stress adenosine myocardial perfusion imaging and the 5-year hard cardiac event rate. Patients were divided into two groups: 
  • Group A: Normal. Patients with an increase in heart rate of 20% or more after adenosine
  • Group B: Abnormal. Patients with an increase of less than 20% after adenosine administration.
RESULTS: During the 5-year follow-up, 3% of patients experienced a hard cardiac event. The heart rate response was independently correlated with cardiac events. Group B (blunted heart rate response) had a 9-fold increased risk of a hard cardiac event, regardless of myocardial perfusion findings. Those with a heart rate response of 40% or greater had the lowest risk, irrespective of perfusion abnormalities.

CONCLUSION: an increase in the heart rate of less 20% after adenosine infusion appears to be an independent predictor of adverse cardiac events. 

CLINICAL IMPLICATION: the heart rate response to vasodilator stress is an indirect marker of cardiac autonomic neuropathy. Advanced cardiac disease is likely to have more cardiac neuropathy and as a result a blunted heart rate response to vasodilator stress with adenosine, and presumably also the other vasodilator agents dipyridamole and regadenoson. I-123 MIBG imaging directly measures sympathetic innervation of the heart, and a fast washout of the tracer is predictive of hard cardiac events in patients with heart failure. This agent has potential to also be a useful prognostic tool in diabetics.

REFERENCE: The heart rate response to adenosine: A simple predictor of adverse cardiac outcomes in asymptomatic patients with type 2 diabetes.: Int J Cardiol. 2012 Sep 12;