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Relationship between heart rate and quiescent interval of the cardiac cycle in children using MRI
Wei Zhang1, Saivivek Bogale2, Farahnaz Golriz3
1E. B. Singleton Department of Pediatric Radiology, Texas Children's Hospital, 6701 Fannin St., Houston, TX, 77030, USA. wxzhang1@texaschildrens.org.
Insights
Pediatric cardiac imaging benefits from identifying optimal quiescent intervals. For heart rates below 80 bpm, diastole offers the longest interval, while systole is best for rates 90 bpm and above.
Area of Science:
- Pediatric cardiology
- Medical imaging
- Cardiac physiology
Background:
- Pediatric cardiac imaging is challenged by constant heart motion.
- Prospective electrocardiography-triggered CT scans require knowledge of optimal cardiac cycle quiescent intervals in children.
Purpose of the Study:
- To evaluate high-temporal-resolution cine MRI in children.
- To determine the relationship between heart rate and optimal quiescent intervals within the cardiac cycle.
Main Methods:
- 225 pediatric patients (ages 0-18) underwent high-temporal-resolution cine MRI.
- Quiescent intervals in systole and diastole were determined for heart rates from 40-178 bpm.
- Statistical analysis compared systolic and diastolic quiescent interval durations.
Main Results:
- Significantly longer quiescent intervals were found in diastole for heart rates <80 bpm and in systole for heart rates >90 bpm (P<.0001).
- For heart rates 80-89 bpm, the diastolic interval was longer but not statistically significant (P=.06).
- A chart of optimal quiescent intervals across heart rates was created for CT imaging.
Conclusions:
- Optimal quiescent intervals for pediatric cardiac imaging differ based on heart rate.
- Diastole is optimal for heart rates <80 bpm; systole is optimal for heart rates ≥90 bpm.
- Heart rates of 80-89 bpm have uniformly short quiescent intervals in both systole and diastole.
Background:
Imaging the heart in children comes with the challenge of constant cardiac motion. A prospective electrocardiography-triggered CT scan allows for scanning during a predetermined phase of the cardiac cycle with least motion. This technique requires knowing the optimal quiescent intervals of cardiac cycles in a pediatric population.
Objective:
To evaluate high-temporal-resolution cine MRI of the heart in children to determine the relationship of heart rate to the optimal quiescent interval within the cardiac cycle.
Materials And Methods:
We included a total of 225 consecutive patients ages 0-18 years who had high-temporal-resolution cine steady-state free-precession sequence performed as part of a magnetic resonance imaging (MRI) or magnetic resonance angiography study of the heart. We determined the location and duration of the quiescent interval in systole and diastole for heart rates ranging 40-178 beats per minute (bpm). We performed the Wilcoxon signed rank test to compare the duration of quiescent interval in systole and diastole for each heart rate group.
Results:
The duration of the quiescent interval at heart rates <80 bpm and >90 bpm was significantly longer in diastole and systole, respectively (P<.0001 for all ranges, except for 90-99 bpm [P=.02]). For heart rates 80-89 bpm, diastolic interval was longer than systolic interval, but the difference was not statistically significant (P=.06). We created a chart depicting optimal quiescent intervals across a range of heart rates that could be applied for prospective electrocardiography-triggered CT imaging of the heart.
Conclusion:
The optimal quiescent interval at heart rates <80 bpm is in diastole and at heart rates ≥90 bpm is in systole. The period of quiescence at heart rates 80-89 bpm is uniformly short in systole and diastole.
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