A study was carried out on ethnically different groups of people in the US to understand the impact of heart rate-reducing drugs on people with bradycardia. The study has revealed that bradycardia by itself is not responsible for death or cardiovascular problems. But, when combined with the intake of medication that lowers the heart rate, these risks can persist.

"We believe doctors should look carefully at people who have really slow heart rates when they're on these medications and consider the possibility that the dose needs adjustment or that other diseases that aren't well controlled need to be addressed," said Dr Alain Bertoni of Wake Forest School of Medicine, Winston-Salem.

He added that people with heart rate lower than 50 beats per minute (bpm) should be cautious. Beta-blockers, digitalis and nondihydropyridine calcium-channel blockers, along with all other antiarrhythmic drugs have been categorized as heart-rate–lowering agents in the report.

The MESA-cohort analysis undertaken by the researchers involved 6733 participants from six regions in the US between 2000 and 2002. These participants did not suffer from any clinical cardiovascular disease and were tracked for over a decade. It was revealed that bradycardia was not responsible for cardiovascular disease in either of the participants who were on heart rate-lowering drug or who were not on any such medication.

Furthermore, during multivariate analysis, with coronary artery calcification as a variable, a J-shaped curve for mortality was obtained for participants who were taking heart rate-lowering medicines. This suggests that mortality increased considerable for those having heart rate lower than 50 bpm or greater than 80 bpm, in comparison to those who had 60-60 bpm. Meanwhile, a more linear pattern was prevalent for those participants who were not consuming heart rate-lowering drugs. However, the research cannot clarify if the outcomes were related to either the core heart disease or heart-rate–modifying medicines.