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Discussion on Repolarization Reserve between Patients with Coronary Heart Disease and Normal Controls
Rubing Kang1, Yitong Li2, Chunmei Gao3
1Department of Cardiology, Heji Hospital Affiliated to Changzhi Medical College, Changzhi, 046011 Shanxi, China.
Insights
Normal controls exhibit a healthy repolarization reserve. Patients with coronary heart disease (CHD) show impaired repolarization reserve, confirmed by coronary angiography (CAG) after treadmill exercise testing (TET).
Area of Science:
- Cardiology
- Electrophysiology
- Diagnostic Testing
Background:
- Assessing cardiac repolarization reserve is crucial for identifying individuals at risk for arrhythmias and sudden cardiac death.
- Coronary heart disease (CHD) can significantly impact cardiac electrophysiological properties, including repolarization.
- Treadmill exercise testing (TET) is a common method for evaluating cardiovascular function under stress.
Purpose of the Study:
- To investigate and compare the repolarization reserve between normal controls (NCs) and patients diagnosed with coronary heart disease (CHD).
- To evaluate the utility of treadmill exercise test (TET) in screening for impaired repolarization reserve.
- To correlate findings from TET with coronary angiography (CAG) results for definitive CHD diagnosis.
Main Methods:
- A cohort of 200 inpatients (67 with myocardial ischemia, 66 suspected myocardial ischemia, 67 normal controls) were recruited between 2010 and 2018.
- Participants underwent treadmill exercise test (TET) with continuous monitoring of heart rate (HR) and QT interval.
- QTc values were calculated using Bazett's correction, and data from pre-exercise, during exercise (90, 120 bpm, max HR), and recovery periods were analyzed. Coronary angiography (CAG) was performed on a subset of patients.
Main Results:
- Normal controls consistently maintained mean QTc values below 452 ms across all measured time points during TET.
- Significant differences in QT intervals were observed at HRs of 90 and 120 bpm during exercise (P < 0.05).
- Statistically significant differences in QTc values were found between groups during various exercise phases (P < 0.05), indicating impaired repolarization reserve in CHD patients.
Conclusions:
- Normal controls possess a robust repolarization reserve, characterized by stable QTc intervals during exercise stress.
- Coronary angiography (CAG) serves as a definitive diagnostic tool to confirm myocardial ischemia and identify patients with CHD among those initially screened by TET.
- Patients with confirmed CHD, particularly those with positive CAG findings, demonstrate a compromised repolarization reserve, highlighting the QT interval's role in assessing ventricular repolarization adaptability.
Objective:
To investigate the repolarization reserve of normal controls (NCs) and patients with coronary heart disease (CHD).
Methods:
From January 1st, 2010 to December 31st, 2018, 200 age- and gender-matched inpatients in the Second Hospital of Shanxi Medical University and Heji Hospital Affiliated to Changzhi Medical College were selected for treadmill exercise test (TET), including 67 patients in the myocardial ischemia group, 66 patients in the suspected myocardial ischemia group, and 67 patients in the normal control group. Coronary angiography (CAG) was performed on 49 of 133 patients in the myocardial ischemia group and the suspected myocardial ischemia group, and 9 positives and 40 negatives were identified. The heart rate (HR) and QT interval of TET examiners before exercise, during exercise (90 beats/min, 120 beats/min, maximum HR), and in the recovery period (1 minute and 3 minutes after exercise) were reviewed, and QTc values were calculated after being corrected by BaZett's.
Results:
The mean QTc values in NCs were all below 452 ms, before exercise, during exercise (90 beats/min, 120 beats/min and maximum HR), and during the recovery period (1 minute and 3 minutes after exercise). The comparison results of the RR interval between the two groups revealed P > 0.05, indicating no statistical significance. Significant differences were present when comparing the QT intervals when the HRs were 90 beats/minute and 120 beats/minute during exercise (P < 0.05). And comparing the QTc values, it was found that the QTc values during different exercise periods were statistically different between groups (P < 0.05).
Conclusions:
NCs have good repolarization reserve. CAG can confirm true myocardial ischemia patients (i.e., patients with CHD) among myocardial ischemia and suspected myocardial ischemia patients screened by TET. Patients with positive CAG have poor repolarization reserve as QT interval represents ventricular repolarization adaptability.
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