T. Jared Bunch, MD

Rhythm of Life

The lowdown on heartbeat disorders

John and Dave Have Similar Lifestyles, Different Resting Heart Rates: So Who’s More At Risk for Heart Failure?

Published Jan 22, 2014

Our resting heart rate tells us a lot about our bodies. When elevated it may reflect stress, anxiety, or a battle with illness. When slow, it may suggest we are calm or relaxed, or that we’ve recently injested a large meal, or that we’re physically fit. Our heart rates can change instantly with any stress that may arise; as such, heart rate is an important component in lie detector tests: elevated, it is often one of the first signs that a truth might not be getting told.

Just as people come in all shapes and sizes, so do heart rates. I am often asked the question. “What is the average heart rate?” I usually say it’s between 65-75 beats per minute (bpm), but normal heart rates can vary as much as 20-30 bpm. On an average clinic day, I will like see patients who have average resting heart rates between 40-100 bpm.

A natural question I get asked is this: If the heart is a muscle that at some point will begin to fatigue and wear down, is it okay to have a higher resting heart rate? This type of questioning led one of my favorite instructors during my cardiology training to conclude, “I only have so many heart beats during my life so I am not going to waste them on exercise.” The good news for exercise enthusiasts is that they may have higher heart rates during exercise, but for the remainder of the day their heart rate is on average much lower.

However, this brings up an interesting question: All things being equal, is a lower heart rate better? For example, one man named John exercises 6 times a week for 45-60 minutes. He does not have high blood pressure or diabetes, and he doesn’t smoke. His average resting heart rate is 72 bpm. Another man named Dave also exercises 6 times a week for the same amount of time, and he also does not have high blood pressure or diabetes, and he doesn’t smoke. His average resting heart rate is 60 bpm. In this example, is Dave at lower risk of heart problems in the future compared to John because his heart rate is lower?

Elevated Heart Rates with High Blood Pressure Predicts Risk of Death

Interesting studies provide us some insight into this question. First, in a study of 4,530 people studied on average of 3 years with a history of high blood pressure, men were 218% more likely to die if their heart rate was elevated and women were 214% more likely to die. These elevated risks were independent of the participant’s age. These mortality risks for men and women with faster heart rates may seem high. This is because the risks were for each elevation of heart rate of 40 bpm. So you are comparing men with an average heart rate of 50 bpm and 90 bpm. Most of the time the differences in peoples resting heart rates are not so extreme. Next, they only included people whowere not taking blood pressure medication. Many of our best blood pressure medications not only lower the blood pressure, but the heart rate as well. However, this was one of the first studies to suggest that elevated heart rate alone may be an important long-term marker of risk.

Elevated Heart Rates with Heart Disease Predicts Risk of Death, Heart Failure, and Heart Attacks

In people who have had an injury to the pumping function of the heart, the body typically responds by raising the heart rate. This is because with each beat of the heart, less blood is pumped to our body’s organs and tissues. These organs and tissues send messages back to the heart that they are undernourished and then the heart rate speeds up. This compensation allows, on average, for the same amount of blood per minute to be delivered throughout our body. Thus, the faster our heart rate after a heart injury, the less pumping function the heart has maintained. For example, if a person has suffered a large heart attack and as a consequence lost 50% or their pumping function, the heart rate needs to double to make up the difference.  In a study of people with a prior heart attack or heart failure history, for every heart rate increase of 5 bpm there was an 8% increase in death, 16% increase in worsening heart failure required hospitalization, and a 7% increased risk of heart attack.

With these two studies we have learned that an elevated heart rate in heart disease or with a risk factor for heart disease (high blood pressure) is a bad sign. However, our example of John and Dave was beyond these studies. This question involved two healthy men that had similar lifestyles but different average resting heart rates.

Elevated Heart Rates In People with No History of Heart Disease

A recent study asked the very question presented about John and Dave. The study included 6,814 men and women between the ages of 45 to 84 years involved in the MESA (Multi-Ethnic Study of Atherosclerosis) study. This was a trial that has far reaching implications, as it was very diverse in race. Obtaining racial diversity in studies is very difficult and when not obtained it can result in results that may be applicable to one race and not another. However the MESA trial included a population that was 38% white, 28% African American, 22% Hispanic, and 12% Chinese American. People were excluded from the study if they have any history of heart disease. Their heart function was studied over time using both ultrasound and MRI scans.

What the authors found was fascinating. For every increase in heart rate of 1 bpm, there was a 4% greater risk for heart failure. The greatest risk was those people with an average heart rate >75 bpm compared to those people with an average heart rate <56 bpm. The risk of heart failure between these two groups was increased over 376% (nearly 4x increased) in the faster heart rate group. The risk was found in both men and women. Interestingly, the risk of heart failure with elevated heart rates was only seen in the White and African American patients. In general, Chinese Americans in particular had very low rates of heart failure. The risks of heart failure in Whites and African Americans persisted despite their cholesterol and the medications they were using.

The studied further tried to answer why the risks of heart failure were increased. The authors found over time that those patients with a higher heart rate had a lower pumping function, and their heart chambers became more dilated. These findings are similar to what we have known in people with previous heart disease. As the pumping function weakens, the heart rate increases. In this study of relatively healthy people, a raise in the heart rate predicted very early detrimental changes in the pumping function of the heart.

So according to this study, Dave is slightly lower risk of heart failure than John simply based upon his resting heart rate.

The Next Steps

If you have read this column and checked your heart rate and then compared it to somebody similar to you, you may either feel some relief of anxiety at this point. A few things you should consider when thinking about this study: First, our heart rate is very dynamic. Our average heart rate changes slightly each day. So if you want to use your average heart rate as a marker of health, collect it a few times a week and always when you are truly rested. That means, don’t take it immediately after you have exercised, been stressed or anxious, etc. Next, our average heart rate can change. Most commonly the heart rate will decrease as we increase our daily activity, and our hearts become more efficient. In addition, avoid frequent exposure to cardiac stimulants that will continually drive up the heart rate. Finally, our heart rate typically increases because of changes to the pumping function of the heart. This means that we need to be diligent in preserving the pumping capacity of our hearts. We do this through very careful control of our blood pressure, avoiding or maximally treating diabetes, identifying or treating sleep apnea if present, minimizing salt intake, stopping smoking to prevent injury to the small and large vessels of the heart, and as always increasing daily activity. By exercising and increasing activity, on average our blood pressure throughout the day is lower so the heart has to generate less force to pump blood.

For prevention, a few simple measures can go a long way in maintaining your heart health.

Comments are closed.