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"Apical thinning": Relations between myocardial wall thickness and apical left ventricular tracer uptake as assessed
Dominik A Steffen1, Andreas A Giannopoulos1, Marvin Grossmann1
1Department of Nuclear Medicine, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, 8091, Zurich, Switzerland.
Background:
A reduction in left ventricular apical tracer uptake (apical thinning) is frequently observed in myocardial perfusion imaging (MPI), yet its cause remains a matter of debate, particularly in perfusion emission tomography (PET). This analysis sought to determine whether apical thinning in PET-MPI is attributable to true anatomical thinning of the left ventricular apical myocardium.
Methods And Results:
We retrospectively analyzed 57 patients without any history or signs of apical myocardial infarction who underwent rest PET-MPI with 13N-ammonia and contrast-enhanced cardiac computed tomography (CT). Semi-quantitative normalized percent apical 13N-ammonia uptake at rest, myocardial blood flow (MBF), and k2 wash-out rate constants were compared to apical myocardial wall thickness measurements derived from CT and base-to-apex gradients were calculated. Apical thinning was found in 93% of patients and in 74% when analysis of normalized apical tracer uptake was confined to end-systole. No significant correlation was found between apical myocardial thickness and apical tracer uptake (r = - 0.080, P = .553), MBF (r = - 0.211, P = .115), or k2 wash-out rate (r = - 0.023, P = .872), nor between apical myocardial thickness and any gradients. A statistically significant but small difference in apical myocardial thickness was observed in patients with moderately to severely reduced apical tracer uptake vs patients with normal to mildly reduced uptake (4.3 ± 0.7 mm vs 4.7 ± 0.7 mm; P = .043).
Conclusions:
Apical thinning is a highly prevalent finding during 13N-ammonia PET-MPI that is not solely attributable to true anatomical apical wall thickness or the partial volume effect. Other factors that yet need to be identified seem to have a more prominent impact.
Insights
Apical thinning in myocardial perfusion imaging (MPI) is common but not solely due to anatomical thinning. Further research is needed to identify other contributing factors for this PET-MPI finding.
Area of Science:
- Cardiology
- Nuclear Medicine
- Medical Imaging
Background:
- Left ventricular apical thinning is a frequent observation in myocardial perfusion imaging (MPI), particularly in positron emission tomography (PET).
- The precise cause of this apical thinning in PET-MPI remains debated, prompting investigation into its anatomical basis.
Purpose of the Study:
- To investigate whether apical thinning observed in 13N-ammonia PET-MPI is caused by actual anatomical thinning of the left ventricular apical myocardium.
- To correlate tracer uptake with myocardial wall thickness and blood flow parameters.
Main Methods:
- Retrospective analysis of 57 patients undergoing rest 13N-ammonia PET-MPI and contrast-enhanced cardiac CT.
- Semi-quantitative analysis of apical tracer uptake, myocardial blood flow (MBF), and k2 wash-out rates.
- Comparison with apical myocardial wall thickness measurements from CT and calculation of base-to-apex gradients.
Main Results:
- Apical thinning was observed in 93% of patients (74% at end-systole).
- No significant correlation was found between apical myocardial thickness and apical tracer uptake, MBF, or k2 wash-out rates.
- A small but significant difference in apical thickness was noted between patients with reduced versus normal/mildly reduced apical tracer uptake.
Conclusions:
- Apical thinning in 13N-ammonia PET-MPI is highly prevalent.
- This finding is not solely explained by anatomical apical wall thickness or partial volume effects.
- Other unidentified factors likely play a more significant role in the observed apical thinning.