Certified Rhythm Analysis Technician (CRAT) Practice Exam

The condition where P-P and R-R intervals widen and narrow with breathing is known as sinus dysrhythmia. This phenomenon is primarily associated with the natural variability in heart rate that occurs with the respiratory cycle, a characteristic known as respiratory sinus arrhythmia. During inhalation, the heart rate tends to increase, causing the intervals to shorten, while during exhalation, it slows down, resulting in wider intervals. This fluctuation is a normal physiological response, particularly more pronounced in young and healthy individuals, and is influenced by the autonomic nervous system, particularly the vagus nerve.

In contrast, sinus tachycardia refers to an increase in heart rate, where the intervals would generally decrease rather than exhibit the variability associated with breathing. Sinus bradycardia indicates a slower heart rate without the same pattern of variability with respiration. Normal sinus rhythm can include P-P and R-R intervals that are consistent but does not specifically exhibit the characteristic widening and narrowing associated with respiratory changes. Therefore, sinus dysrhythmia is the correct choice, as it directly correlates with changes in heart rate that occur with breathing patterns.