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How Exercise Strengthens — and Changes — An Athlete’s Heart

Some cardiologists get pumped up about athletes’ hearts — literally. We spoke with Naveed A. Naz, MD, cardiologist at VCU Health Pauley Heart Center, about his work in sports cardiology. Dr. Naz shares with us the difference between an athletically adapted heart and a pathological heart.

African-American woman running along a beach

Just because someone is “in shape” doesn’t mean their heart is.

Athletes exercise regularly, but even they can’t assume their heart is healthy. Even the most dedicated athletes can experience heart problems — and that’s where sports cardiology comes in. To learn more about how every athlete’s heart is unique, we talked with Naveed A. Naz, MD, a noninvasive general cardiologist at VCU Health Pauley Heart Center who specializes in sports cardiology.

As a noninvasive cardiologist, Dr. Naz performs advanced structural imaging on an outpatient basis. His time in the military identifying cardiovascular abnormalities in active-duty soldiers prepared him for his work at VCU Health Pauley Heart Center with highly athletic patients eager to get back to peak competition shape. Here’s what he had to say.

What is sports cardiology?

We all have unique hearts and exercise routines to support our cardiovascular health. But did you know your heart muscle changes from your first attempts at a sport or exercise to training for competition? Like any other muscle in your body, your heart gets stronger the more it’s exercised — and sports cardiologists like Dr. Naz identify these physiological adaptations to the heart.

Dr. Naz describes his specialty as “discerning athletic hearts from pathological hearts,” or distinguishing the physiological adaptations of athletic hearts from abnormalities that may require medical treatment. His diagnostic testing is an integral first step for patients prior to valve replacements or other advanced heart procedures.

Why would an athlete consult a cardiologist?

Patients often come to Dr. Naz when they’re no longer achieving their usual athletic landmarks. For instance, if a runner who normally clocks a five-minute mile can now only run a seven-minute mile, this may be due to an underlying heart condition. Other symptoms that warrant athletic concern for Dr. Naz are chest pain, heart palpitations (a fast or irregular heartbeat that doesn’t slow down appropriately) or unexplained fainting.

“[In my work] I try to judiciously decide who has life-threatening pathology and minimize unnecessarily restricting athletes,” says Dr. Naz.

Sports cardiologists typically evaluate a patient’s family history to help inform a diagnosis. If there’s evidence of cardiovascular disease or if a relative died suddenly of cardiac arrest, the patient — no matter how much they exercise — is more at risk for heart disease. Many of the athletes Dr. Naz sees have hypertrophic cardiomyopathy (HCM), a genetic condition where the heart muscle becomes too thick, so it struggles to pump blood throughout the body.

Dr. Naz sees athletes primarily through referrals from sports family practitioners or sports medicine physicians. More recently, he’s been working with patients focused on post-COVID-19 recovery on how to safely return to their normal athletic activities.

What is involved in the diagnostic process?

Dr. Naz begins by measuring the athlete’s functional capacity through — you guessed it — exercise. He often starts his patients on a treadmill while they’re attached to an electrocardiogram, or an EKG, which shows the changes in a heart’s electrical activity that are generated each time it pulses. The results from the EKG can help Dr. Naz establish a baseline diagnosis.

“That [treadmill] gives us a lot of insight about their peak functional status and whether they have any electro abnormalities or dysrhythmias,” says Dr. Naz.

Depending on the symptoms a patient presents, Dr. Naz may also take an echocardiogram, or an ultrasound of the heart. Through sound wave technology, an echocardiogram helps measure a patient’s cardiac function, heart chamber sizes and valvular function and provides his team with other relevant data.

Electrocardiogram (EKG), echocardiogram and baseline 12-lead electrocardiogram (ECG) “are the three major tools that help us stratify where the athlete is in the cardiovascular realm,” says Dr. Naz.

What does an athletically adapted heart look, sound and feel like?

According to Dr. Naz, a key identifier of a healthy heart in an athlete is symmetric chamber dilatation. This means all four of the heart’s chambers are symmetrically enlarged. Athletically adapted hearts typically have dilated chambers (meaning they can recover from stress to a resting state quickly) and a low resting heart rate.

“What I look for are bigger hearts that are beating more slowly and have big stroke volumes,” says Dr. Naz. People with large stroke volumes pump a lot more blood out of the left ventricle and throughout the body with each pulse.

To determine the heart’s health, Dr. Naz will measure its ejection fraction — the percentage of blood that leaves the ventricles at each contraction. For patients who regularly exercise, the ejection fraction of their heart’s ventricular function goes down when they’re at rest. Dr. Naz also looks at diastolic function, or how quickly the heart’s ventricles relax.

“Athletes have some of the most robust ventricular relaxation. Their hearts are so energy efficient — they just pop right open and accept more blood. And we can study that on an ultrasound of the heart,” says Dr. Naz.

What are some pathologic heart adaptions cardiologists look out for?

Sometimes these tests will show pathologic heart abnormalities. Sports cardiology specialists like Dr. Naz look out for “asymmetric chamber dilatation, where just the left ventricle is big and the other chambers are small, or just the atria are big and the ventricular chambers are small.” Asymmetric chamber dilatation can lead to dilated cardiomyopathy (DCM), a type of heart disease where the heart’s chambers get too enlarged and can no longer contract.

Dr. Naz also studies ventricular function to detect if there is excessive wall thickness around the ventricles through an electrocardiograph (EKG), echocardiogram or magnetic resonance imaging (MRI). For someone with a condition called hypodermic cardiomyopathy, or a thickening or stiffening of the heart, a cardiologist might see ventricular wall thickness within the left ventricle. Or, if a patient has right ventricular hypertrophy, Dr. Naz can detect dilation in the right ventricle.

“If we’re ever concerned, we can ask the athlete to de-train, to take a week off and to slow down. And a lot of times, you see the heart return to its normal parameters,” explains Dr. Naz. While this isn’t ideal for the avid athletes he sees, when the heart returns to normal after rest, “we know retrospectively that [the enlarged chambers] was just an athletic adaptation.”

Depending on the results of the tests, Dr. Naz will work alongside patients and the rest of the cardiologist team at VCU Health Pauley Heart Center to get the care they need, so they can safely get back to the activities they enjoy.

Whether you’re a super athlete who frequently competes or you participate in sports as a hobby — if you’re exercising regularly, then so is your heart. Have questions about heart health and exercise? Schedule an appointment with Naveed A. Naz, MD, or any other members of our sports cardiology team at VCU Health Pauley Heart Center.