National Center for Competency Testing (NCCT) Medical Assistant Practice Test

What indicates that the heart is functioning normally on an ECG?

1. Regular R-R intervals

2. Inverted T-waves

3. Variable heart rates

4. Widened QRS complexes

The correct answer is: Regular R-R intervals

The presence of regular R-R intervals on an electrocardiogram (ECG) is a key indicator that the heart is functioning normally. R-R intervals represent the time between consecutive R waves of the QRS complex, which signals the heart's ventricular depolarization. Regular intervals suggest a stable and consistent rhythm, meaning that the heart is beating in a coordinated manner without arrhythmias or irregularities. This stability is essential for proper cardiac output and overall cardiovascular health. In contrast, inverted T-waves can signify issues such as myocardial ischemia or electrolyte imbalances, variable heart rates may indicate arrhythmias or autonomic nervous system influences, and widened QRS complexes often suggest a delay in ventricular conduction, which can be a sign of underlying heart problems. All these abnormalities indicate potential dysfunction in heart rhythm or conduction, contrasting with the normalcy suggested by regular R-R intervals.