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Heart rate response during exercise testing and ambulatory ECG monitoring in patients with syndrome X
A R Galassi1, J C Kaski, F Crea
1Cardiovascular Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, England.
Insights
Patients with syndrome X exhibit distinct heart rate patterns during exercise and daily life compared to coronary artery disease patients and healthy individuals. These differences in heart rate response may aid in understanding syndrome X.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Syndrome X, characterized by angina pectoris with normal coronary arteries, presents a diagnostic challenge.
- Understanding the heart rate response in syndrome X is crucial for differentiating it from coronary artery disease (CAD).
Purpose of the Study:
- To compare heart rate responses during exercise testing and 24-hour ambulatory electrocardiographic (ECG) monitoring in patients with syndrome X, CAD, and healthy subjects.
- To identify unique heart rate patterns associated with syndrome X.
Main Methods:
- Exercise testing and 24-hour ambulatory ECG monitoring were conducted on 26 patients with syndrome X, 27 with CAD, and 21 healthy controls, all without antianginal treatment.
- Heart rate response was analyzed using the heart rate/time slope (exercise) and mean diurnal heart rate (ambulatory monitoring).
Main Results:
- Patients with syndrome X showed a significantly lower heart rate/time slope during exercise compared to healthy subjects, but similar to CAD patients.
- The intercept of the heart rate/time slope, resting pre-exercise heart rate, and mean diurnal heart rate were significantly higher in syndrome X patients than in both CAD patients and healthy subjects.
- These findings indicate altered autonomic regulation or chronotropic incompetence in syndrome X.
Conclusions:
- Syndrome X is associated with distinct heart rate dynamics, including higher resting and diurnal heart rates and altered exercise heart rate response.
- These findings suggest potential differences in cardiovascular autonomic regulation between syndrome X and CAD.
- Further research into the pathophysiology of syndrome X is warranted based on these heart rate response characteristics.
Abstract:
The response of the heart rate during exercise testing and 24-hour ambulatory electrocardiographic (ECG) monitoring performed with patients not receiving antianginal treatment was assessed in 26 patients (9 men and 17 women; mean age 51 +/- 8 years) with syndrome X (angina pectoris with normal coronary arteries), in 27 patients with coronary artery disease (10 men and 17 women; mean age 55 +/- 9 years), and in 21 healthy subjects (8 men and 13 women; mean age 47 +/- 11 years). In patients with syndrome X the slope of the regression line of heart rate versus time (heart rate/time slope) during exercise testing was similar to that of patients with coronary artery disease (3.3 +/- 0.8 versus 3.1 +/- 1.2 beats/min), but significantly lower than that in healthy subjects (4.2 +/- 1.1 beats/min; p less than 0.003). In patients with syndrome X the intercept of the heart rate/time slope was significantly higher than that in coronary artery disease patients and healthy subjects (102 +/- 15, 86 +/- 18, and 90 +/- 16 beats/min, respectively; p less than 0.015). Resting preexercise heart rate was also significantly higher in syndrome X, compared with coronary artery disease patients and healthy subjects (91 +/- 16, 79 +/- 16, and 80 +/- 14 beats/min, respectively). During ambulatory ECG monitoring, mean diurnal heart rate (from 6 AM to 6 PM) was higher in patients with syndrome X (83 +/- 8 beats/min) than in patients with coronary artery disease (75 +/- 8 beats/min) and healthy subjects (74 +/- 11 beats/min) (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)