The average heart beats 100,000 to 120,000 times each day. And since the average person in the United States will live into their mid- to late-seventies, this means your heart will beat over two billion times in your life. To accomplish all of this pumping, your heart develops specialized pacemaker cells and conduction tissues that conveys electrical impulses across your heart.
Despite their critical role, these specialized conductive tissues are delicate. They also age, and in some people they can stop working and cause heart disease. New research shows that a common treatment for high blood pressure (hypertension) may help keep the heart's electrical system healthy as you get older.
How Your Heart's Electrical System Works
The electrical impulse of your heart begins in the right upper chamber from a group of specialized pacemaker cells called the sinoatrial (SA) node. The electrical impulse is quickly carried across both upper heart chambers: the atria. When heart muscle cells are stimulated by electricity, they contract, or squeeze. The two upper chambers squeeze in unison and pump blood into the two lower heart chambers: the ventricles.
The electrical signal is collected in the middle of the heart in a relay center called the atrioventricular (AV) node. Then, through long specialized electrical tracts called the right and left bundle branches, the electricity is delivered to the bottom portion of the ventricles, which then squeeze from the bottom up and push the blood out to the great arteries of your body.
What Is Electrical Heart Block?
When most people think about heart blockages, they see images of blocked arteries from cholesterol plaques that can cause a heart attack (myocardial infarction). But a completely separate blockage that involves the heart's electrical system — a heart block — can develop along all levels of the conduction systems and on multiple levels: in the AV or SA node, or in the bundle branches (parts of the heart’s electrical system that deliver impulses to your ventricles).
If you experience a heart block, you may experience some of the following:
- Chest discomfort
- Shortness of breath
- Exercise intolerance
- Syncope (temporary loss of consciousness, or fainting)
Unfortunately, once disease develops in the heart's conduction system, it often progresses with no known medical therapies to improve it. If you develop heart block and have symptoms, or if the upper and lower heart chambers of your heart no longer communicate electrically, you may need a surgically implanted pacemaker. This device, which delivers small electrical impulses to your upper and lower heart chambers, replaces any missed beats from the diseased conduction system or from significant delays or blocks in electrical communication.
You may know someone who has a pacemaker. Between 1993 and 2009, about three million U.S. patients received a pacemaker for symptomatic electrical heart block, according to a survey published in the Journal of the American College of Cardiology in October 2012. During the study time, the use of pacemakers increased by 56 percent — a trend that continues today as our society ages, and people live longer with heart disease.
Risk Factors for Electrical Heart Block
Risk factors for heart block include:
- High blood pressure
- Heart valve disease
- Heart infection
- Heart attack
- Heart failure
- Having heart surgery
The most common risks are aging and high blood pressure. And while you can’t do much about aging, you can do something about high blood pressure. Depending on how you treat it, you may lower your risk of conduction system disease.
How High Blood Pressure Treatment Can Help
Doctors treat high blood pressure in many different ways, some of which I've covered in previous columns, like being careful not to eat too much salt. In addition to lifestyle changes, multiple blood pressure medications called anti-hypertensive agents can be used to treat the disease and prevent progression and complications.
All blood pressure medications lower your blood pressure, but drugs like beta-blockers and calcium channel blockers also lower heart rate. And some, like diuretics, lower fluid levels in the body and can decrease edema (swelling). Still others, such as ACE inhibitors or angiotensin receptor blockers (ARBs), can impact the body's inflammatory response and decrease fibrosis or cell breakdown.
Research: ACE Inhibitors Lower Risk of Heart Block
With these unique aspects of blood pressure medications in mind, and knowing that high blood pressure can result in early conduction system disease, researchers asked which medications might lower blood pressure and also decrease risk of conduction system disease.
The Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) included 21,004 patients ages 55 and older who had high blood pressure and one other heart disease risk factor, such as high cholesterol, diabetes, coronary artery disease, or a history of smoking. The patients were either treated with an ACE inhibitor lisinopril; a calcium channel blocker, Norvasc (amlodipine besylate); or a diuretic, Thalitone (chlorthalidone) and a statin drug, Pravachol (pravastatin) for their high cholesterol. ALLHAT results were published in JAMA Internal Medicine in June 2016.
Researchers followed the patients for up to eight years to look for heart disease and found that 1,114 people developed heart block. These included 570 patients with a complete right bundle branch block, and 389 with a complete left bundle branch block.
Being older increased the risk of developing conduction system disease by 47 percent in this group of patients with high blood pressure, and was the strongest predictor that they would develop a heart block.
In this study, statins didn't lower a person's risk of conduction system disease. But using the ACE inhibitor lisinopril lowered risk of electrical conduction disease by 19 percent compared to the diuretic, and by 14 percent compared to the calcium channel blocker.
This large study of older adults also confirmed that high blood pressure and age present unique challenges to the heart's electrical system, and that conduction abnormalities commonly develop. But for the first time, we have insight into a potential way to prevent or significantly lower the risk of conduction system disease in people who have high blood pressure by using a commonly prescribed drug.
Photo: Dmitry Fisher/Getty Images
Important: The views and opinions expressed in this article are those of the author and not Everyday Health.