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[Left ventricular diastolic performance in patients with myocardial infarction: assessment with backward method of
Insights
A new backward method for radionuclide angiography reliably assesses left ventricular (LV) diastolic function in myocardial infarction (MI) patients. This technique is more sensitive than ejection fraction for detecting diastolic abnormalities.
Area of Science:
- Cardiology
- Nuclear Medicine
- Biomedical Engineering
Background:
- Radionuclide angiography is used to assess left ventricular (LV) diastolic performance in myocardial infarction (MI) patients.
- The conventional ECG-triggered method for obtaining LV volume curves is unreliable due to respiratory arrhythmia, particularly for late diastolic measurements.
Purpose of the Study:
- To evaluate the reliability of a new backward ECG-gated radionuclide angiogram method for diastolic LV volume curves.
- To determine the availability of Phase 1 max and Phase 3 max as sensitive indexes of LV diastolic performance in MI.
Main Methods:
- Compared LV volume curves and dV/dt curves using conventional and backward ECG-gated radionuclide angiogram methods in 29 cases.
- Analyzed LV dV/dt curves from the backward method in 8 controls and 28 MI patients.
- Defined Phase max as maximum dV/dt within specific diastolic phases, corrected for end-diastolic counts.
Main Results:
- The backward method showed high correlation with the conventional method for ejection fraction (EF) and Phase 1 max, but not Phase 3 max.
- Phase 1 max was reduced earlier than EF decrease, and Phase 3 max increased prior to EF decrease in MI patients.
- MI patients exhibited abnormal early diastolic filling and increased late diastolic atrial contraction, suggesting impaired LV suction and atrial function limitations.
Conclusions:
- The backward ECG-gated radionuclide angiogram method provides a reliable assessment of diastolic LV volume curves.
- Phase 1 max and Phase 3 max are more sensitive indicators of LV diastolic dysfunction in MI than EF.
- Abnormalities in early diastolic filling and atrial contraction highlight the complexities of diastolic dysfunction in MI.
Abstract:
Radionuclide technique in the evaluation of left ventricular (LV) diastolic performance has been applied in patients with myocardial infarction (MI). But the late diastolic LV volume curve obtained from the radionuclide angiogram is unreliable, whenever we sum up radioactivities by ECG-triggered method (conventional method) because of respiratory arrhythmia. The purpose of the present study was (1) to estimate the reliability of diastolic LV volume curve obtained from the radionuclide angiogram by our new method (backward method: backward ECG-gated radionuclide angiogram to the preceding R wave), and (2) to determine the availability of Phase 1 max and Phase 3 max as the indexes of LV diastolic performance. We analyzed LV volume curve and its dV/dt curve in 29 cases by both conventional and backward methods. The LV diastolic period was equally divided into three time intervals. The early, mid and late trisections of the diastolic period were expressed as phase 1, phase 2 and phase 3, respectively. A Phase max was defined as maximum dV/dt in the phase corrected for end-diastolic counts. At first, ejection fraction (EF), Phase 1 max, Phase 2 max and Phase 3 max were compared between the two different methods to estimate the reliability of diastolic LV volume curve obtained from a backward method. The backward method correlated well with the conventional method regarding EF and Phase 1 max (r = 0.965 and r = 0.940, respectively), but there was no correlation regarding Phase 3 max. This indicated that LV diastolic volume curve obtained from the backward method was reliable. In the second place, we analyzed LV dV/dt curve obtained from the backward method in 8 controls and 28 MI patients to determine the availability of Phase max as the indexes of LV diastolic performance. Phase 1 max was reduced earlier than a decrease of EF, and Phase 3 max was increased prior to a decrease of EF in MI. These data indicated that Phase 1 max and Phase 3 max as the indexes of LV diastolic performance were more sensitive than the indexes of LV systolic performance. Also MI patient had an abnormality in early diastolic filling and an increased atrial contraction in late diastolic filling of the left ventricle. The mechanism of abnormal LV early diastolic filling, even in the absence of abnormal systolic function, might be impaired LV suction because of fibrosis or the relatively ischemic myocardium. In mild to moderate LV failure atrial contraction compensated abnormal early diastolic filling, but there was no such a compensation in severe LV failure. It may suggest the limitation of atrial function as a booster pump.