In one study, people with pre-hypertension were randomly assigned to augment their drug treatment with either a course in mindfulness meditation or a program that taught progressive muscle relaxation. Those who learned mindfulness had significantly greater reductions in their systolic and diastolic blood pressure than those who learned progressive muscle relaxation, suggesting that mindfulness could help people at risk for heart disease by bringing blood pressure down.
In another study, people with heart disease were randomly assigned to either an online program to help them practice meditation or to a waitlist for the program while undergoing normal treatment for heart disease. Those who took the mindfulness program showed significant improvements on the six-minute walking test (a measure of cardiovascular capacity) and slower heart rates than those in the waitlist group.
While one review of randomly controlled studies showed that mindfulness may have mixed effects on the physical symptoms of heart disease, a more recent review published by the American Heart Association concluded that, while research remains preliminary, there is enough evidence to suggest mindfulness as an adjunct treatment for coronary disease and its prevention.
Mindfulness may also be good for hearts that are already relatively healthy. Research suggests that meditating can increase respiratory sinus arrhythmia, the natural variations in heart rate that happen when we breathe that indicate better heart health and an increased chance of surviving a heart attack.