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Gated versus first-pass radioangiography in the evaluation of left-to-right shunts
D Eterović1, Z Dujić, S Popović
1Department of Nuclear Medicine, Clinical Hospital Split, Croatia.
Insights
The stroke count method and gamma fit technique evaluate left-to-right shunts. Gamma fit excels with small shunts, while the stroke count method is accurate for larger shunts (QP/Qs ≥ 2).
Area of Science:
- Cardiology
- Medical Imaging
- Pediatric Cardiology
Background:
- Left-to-right shunts are common congenital heart defects.
- Accurate quantification of pulmonary-to-systemic flow ratio (QP/Qs) is crucial for diagnosis and management.
- Gated radioangiography offers a non-invasive method for assessing cardiac function and shunts.
Purpose of the Study:
- To compare the efficacy of the stroke count method and the gamma fit first-pass technique in evaluating left-to-right shunts.
- To assess the accuracy of these methods against oximetry data.
- To determine the optimal application of each method based on shunt size.
Main Methods:
- Utilized gated radioangiography to obtain left ventricular stroke counts (SCLV) and right ventricular stroke counts (SCRV).
- Calculated the pulmonary-to-systemic flow ratio (QP/Qs) using both the stroke count method (SCRV/SCLV or SCLV/SCRV) and the gamma fit first-pass technique.
- Compared results with oximetry data in 17 patients with left-to-right shunts.
Main Results:
- The stroke count method showed moderate correlation with oximetry (r = .71).
- The gamma fit method demonstrated a stronger correlation with oximetry (r = .87).
- The gamma variate method was superior for detecting and estimating small shunts; the stroke count method showed better agreement for QP/Qs ≥ 2.
Conclusions:
- Both stroke count and gamma fit methods are viable for assessing left-to-right shunts.
- The gamma fit method is more accurate for small shunts.
- The stroke count method provides reliable data for larger shunts (QP/Qs ≥ 2).
Abstract:
Excluding regurgitant ventricles and multiple shunting, left-to-right shunts of the central circulation can be evaluated from the difference between the right ventricular stroke counts (SCRV) and the left ventricular stroke counts (SCLV), which are obtained from gated radioangiography. The pulmonary-to-systemic flow ratio (QP/Qs) is equated to SCRV/SCLV in atrial shunts and to SCLV/SCRV in ventricular and ductal shunts. In this paper, the potentials of the stroke count method have been compared to the gamma fit first-pass technique, incorporating the recent refinements in ductal shunts and deconvolution of the pulmonary curve. In 17 patients with left-to-right shunt, the stroke count method and the gamma fit method correlated moderately with oximetry (r = .71 and .87), respectively. The gamma variate method appeared superior in the detection and estimation of small shunts, whereas when QP/Qs was two or larger, the stroke count method yielded closer agreement with oximetry data.