Electrical problems in the heart such as left ventricular conduction disease can often lead to serious and fatal complications. Treatment to lessen its effects involves implanting a permanent pacemaker, but there are no proven preventive strategies at present.
In a study published in JAMA Cardiology, researchers took advantage of a prospective trial in which individuals with hypertension were randomly assigned to standard and aggressive blood pressure (BP) control. They found that intensive BP control is associated with lower risk of left ventricular conduction disease, indicating left ventricular conduction disease may be preventable.
“This research was motivated by patients who came in with complete heart block where I put in a pacemaker and they asked, ‘Why did this happen to me?’” said senior author Gregory Marcus, cardiologist and UCSF professor of medicine. “The answer to this question has not been clear, so we wanted to look at the impact that blood pressure might have on the development of their conduction disease.”
The authors performed a statistical analysis of the previously completed Systolic Blood Pressure Intervention Trial (SPRINT) to determine the association between targeting intensive BP control and the risk of developing left ventricular conduction disease. Participants included in the five year long SPRINT trial were adults 50 years and older with hypertension and at least one other cardiovascular risk factor. Participants with early signs of left ventricular conduction disease, ventricular pacing or ventricular pre-excitation were excluded from the analysis.
Participants were randomly assigned to either normal blood pressure control (targeting a systolic blood pressure less than 140) or a more aggressive BP control (targeting a BP less than 120). As part of the analysis, the authors reviewed the serial ECGs that the participants received over the course of the trial and found that those randomly assigned to the more aggressive BP control experienced significantly less conduction disease on the left side of the heart.
“This analysis suggests that more aggressive BP control might be a way to prevent this sort of common disease,” said Marcus. “More broadly, the use of randomised controlled trial data provided compelling evidence that this common disease is not an immutable fate, but that the risk can be modified.”
By contrast, the researchers saw no differences in right-sided conduction disease (manifested by right bundle branch blocks). The authors considered right bundle branch blocks as a “negative control” since the right side of the heart is not directly affected by BP control and as such bundle branch blocks are not generally associated with the same severe outcomes as left bundle branch blocks.
The authors note that SPRINT did not examine the role of anti-hypertensive drugs, suggesting further research into associations between specific medications and conduction disease rates may be warranted.
