Significance of Cardiac Autonomic Dysfunction in the Diagnosis of Cardiac Diseases 2001.3.14

Significance of Cardiac Autonomic Dysfunction in the Diagnosis of Cardiac Diseases 2001.3.14

1. Clinical manifestations of cardiac autonomic dysfunction

① Prolonged QT interval, reflecting decreased bundle branch conduction function, indicates cardiac autonomic dysfunction.

② Orthostatic hypotension, also known as orthostatic collapse, indicates cardiac autonomic dysfunction.

③ Large heart rate variability indicates autonomic dysfunction.

④ Hypertension or hypotension.

⑤ Cardiomyopathy.

⑥ Angina pectoris.

⑦ Myocardial infarction.

2. Methods for detecting cardiac autonomic dysfunction

Standard Cardiac Autonomic Function Test (SCFT) requires subjects to abstain from smoking, tea, alcohol, or coffee the night before the test and to cooperate fully.

① Valsalva maneuver: The patient blows air into a blood pressure cuff to 40 mmHg and holds it for 15 seconds, while simultaneously recording the ECG to calculate the ratio of the longest R-R interval to the shortest R-R interval. A normal value of 1.11–1.20 is considered positive.

② Deep breathing test: Perform six deep breaths per minute while monitoring the ECG; the fastest and slowest heart rates should be between 11 and 14 beats per minute. A value below 10 beats per minute is considered positive.

③ Change in heart rate from lying to standing position: If the R-R interval changes by less than 1.00, it is considered positive.

④ Change in systolic blood pressure from lying to standing position greater than 30 mmHg is considered positive. These tests indicate that the regulatory function of the cardiac autonomic nervous system has been disrupted and can no longer compensate for changes in conditions. During forced inflation, deep breathing, and positional changes, the heart rate changes are smaller than normal, indicating poor compensatory function; large fluctuations in blood pressure suggest that the heart’s ability to maintain normal blood pressure is also impaired.