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Quantification of the atrial contribution to diastolic filling during radionuclide angiography
H J Muntinga1, F van den Berg, H R Knol
1Department of Cardiology, Martini Hospital, Groningen, The Netherlands.
Insights
The PQ-interval on an electrocardiogram is a more reliable indicator of atrial contraction onset than the atrial contribution (AC) interval derived from radionuclide angiography. This study found the AC-interval often exceeds the PQ-interval, revealing passive filling before atrial contraction.
Area of Science:
- Cardiology
- Nuclear Medicine
- Physiology
Background:
- Atrial contraction significantly contributes to left ventricular filling.
- Precisely defining the onset of atrial contribution to ventricular filling is crucial for understanding cardiac dynamics.
- Existing methods for timing atrial activity may have limitations.
Purpose of the Study:
- To precisely define the onset of late diastolic filling relative to atrial contraction.
- To quantify the atrial contribution (AC) to left ventricular filling using radionuclide angiography.
- To compare the timing of atrial activity derived from radionuclide angiography with electrocardiogram (ECG) parameters.
Main Methods:
- Quantified atrial contribution (AC) to left ventricular filling in 34 patients using radionuclide angiography.
- Constructed a flow-volume loop from the time-activity curve and its first derivative.
- Defined the AC-interval from minimal flow to maximal end-diastolic counts and correlated it with the PQ-interval on the ECG.
Main Results:
- Relative filling volumes within the AC-interval and PQ-interval were highly correlated (r = 0.99, P < 0.0001).
- The PQ-interval and AC-interval showed a significant correlation (r = 0.82, P < 0.0001).
- In some patients, the AC-interval was longer than the PQ-interval, indicating passive filling before atrial contraction, especially at lower heart rates.
Conclusions:
- The PQ-interval on the ECG is a more accurate marker for the onset of atrial activity during radionuclide angiography than the AC-interval.
- The AC-interval may include passive diastolic filling (diastasis) preceding atrial contraction.
- Understanding these timing differences is important for accurate cardiac function assessment.
Abstract:
To define exactly the onset of late diastolic filling with respect to atrial contraction, the atrial contribution (AC) to left ventricular filling was quantified in 34 patients with a variety of diseases using radionuclide angiography. From the time-activity curve and its first derivative, a flow-volume loop was constructed. Using the flow-volume loop, the period between minimal flow and the moment of maximal end-diastolic counts was defined as the AC-interval and correlated with the PQ-interval on the electrocardiogram. The relative filling volumes within these time periods were closely related in all patients (r = 0.99, P < 0.0001). The correlation between the PQ-interval and AC-interval was also statistically significant (r = 0.82, P < 0.0001). In a subset of patients, the PQ-interval and AC-interval were not exactly the same. In these patients, the AC-interval was always longer than the PQ-interval, indicating the existence of passive diastasis flow before the onset of atrial contraction. This was more apparent in patients with low heart rates than in those with high heart rates. Despite the close correlation between the PQ-interval on the electrocardiogram and the AC-interval of the flow-volume loop, they may represent different entities. We conclude that the PQ-interval is better than the AC-interval for determining the moment of onset of atrial activity during radionuclide angiography.