Impact of scar on SPECT assay of left ventricular contraction dyssynchrony
Daniel R Ludwig1, Mati Friehling, Erik B Schelbert
1Heart, Lung, and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA.
Insights
Left ventricular scar burden can falsely elevate phase standard deviation (PSD) in patients undergoing cardiac resynchronization therapy (CRT) selection. This finding is crucial for accurately assessing CRT candidacy in ischemic cardiomyopathy patients.
Area of Science:
- Cardiology
- Medical Imaging
- Biomedical Engineering
Background:
- Many patients undergoing cardiac resynchronization therapy (CRT) do not respond, particularly those with ischemic cardiomyopathy and significant left ventricular (LV) scar burden.
- Current CRT selection criteria may not accurately assess CRT-remediable LV dyssynchrony.
- Phase analysis of gated single photon emission computed tomography (SPECT) is a promising tool for quantifying dyssynchrony, but its performance in the presence of scar requires evaluation.
Purpose of the Study:
- To evaluate the impact of left ventricular (LV) scar on phase analysis of gated single photon emission computed tomography (SPECT) for assessing cardiac resynchronization therapy (CRT) candidacy.
- To determine if LV scar artifactually increases phase standard deviation (PSD) measurements in patients with ischemic cardiomyopathy (ICM).
Main Methods:
- Consecutive patients with ischemic (ICM, n=50) or non-ischemic (NICM, n=39) cardiomyopathy underwent pre-CRT SPECT imaging.
- Phase analysis was performed on raw SPECT images to calculate phase standard deviation (PSD), a measure of dyssynchrony.
- For ICM patients, image data were reanalyzed after removing scarred segments to assess scar's impact on PSD.
Main Results:
- Raw image analysis revealed significantly higher PSD in ICM patients (57±17°) compared to NICM patients (35±13°, p<0.001).
- In ICM patients, PSD decreased significantly (40±13°, p<0.001) after stripping scarred segments.
- Scarred segments exhibited low-amplitude, random signals, suggesting noise rather than myocardial contraction.
Conclusions:
- Phase standard deviation (PSD) values derived from SPECT imaging may be spuriously elevated by left ventricular scar.
- These findings are critical for accurate patient selection for cardiac resynchronization therapy (CRT), especially in ischemic cardiomyopathy.
- Revising SPECT analysis to account for scar may improve the reliability of CRT selection criteria.
Purpose:
Many patients presently receiving cardiac resynchronization therapy (CRT) do not respond. A disproportionate number of nonresponders have ischemic cardiomyopathy, with significant left ventricular (LV) scar burden. Current selection criteria, such as electrocardiography or echocardiography, may not reliably portray the magnitude of CRT-remediable LV contraction dyssynchrony. Although phase analysis of gated single photon emission computed tomography (SPECT) image data is increasingly appreciated as a tool for quantifying dyssynchrony, its use in the setting of scar has not been adequately evaluated.
Methods:
Consecutive patients with ischemic (ICM, n = 50) or nonischemic (NICM, n = 39) cardiomyopathy underwent SPECT imaging prior to receiving CRT. In each patient, phase analysis of the raw images was performed to yield a phase standard deviation (PSD), an index which varies directly with the magnitude of dyssynchrony. ICM patient image data were also reanalyzed after scarred segments were stripped away.
Results:
Raw image analysis demonstrated that PSD was significantly larger among ICM (57 ± 17°) than NICM (35 ± 13°, p < 0.001) patients. Among ICM patients, PSD after stripping of scarred segments was significantly decreased (40 ± 13°, p < 0.001). Signals emanating from scarred segments were of low amplitude and presented a random pattern, suggestive of noise rather than indicating contraction.
Conclusion:
PSD values may be spuriously increased by scar. These findings may be important when using SPECT in selecting ischemic cardiomyopathy patients for CRT.
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