Assessment of Left Ventricular Structural Abnormalities
The high spatial resolution and excellent field of view of CCT enables it to depict a range of myocardial, septal, and other structural lesions.
Myocardial crypts (or clefts) have been defined as discrete V-shaped extensions of the blood pool inserting more than 50% into the compact myocardial wall that tend to be less visible during systole and are not associated with local hypokinesis or dyskinesia. Increased prevalence of crypts has been reported in carriers of the gene for hypertrophic cardiomyopathy (as much as 81%). However, myocardial crypts also are seen in normal subjects, so their precise significance has yet to be determined.
Congenital left ventricular (LV) diverticula are rare cardiac malformations characterized as outpouchings of the myocardium and can be fibrous or muscular. The prevalence has been reported between 0.02% and 0.04%. They are associated with other congenital abnormalities in about 70% of cases. Muscular diverticula typically are apical and have a full-thickness myocardial wall with preserved systolic contraction. Diverticula can be differentiated from crypts or clefts by a narrow mouth but a wide outpouching extending beyond the normal LV margins. Cardiac CT (CCT) has been proposed as useful for differentiating aneurysm from pseudoaneurysm by exclusion of coronary artery disease, visualization of the LV wall layers, and dynamic assessment of regional wall function ( Fig. 20-3 ).
Post-Infarction Ventricular Pseudoaneurysms, Septal Rupture, and Intramyocardial Hematoma
Pseudoaneurysms are an uncommon complication of acute myocardial infarction, occurring in less than 1% of cases. Cardiac surgery, penetrating or other trauma, and infection also can lead to the development of these abnormalities. The excellent spatial resolution of CT should be ideal for identifying the myocardial wall disruption. Single case reports have demonstrated the ability of CCT to depict post-infarction ventricular pseudoaneurysms, and coronary anatomy.
Post-infarction septal rupture and intramyocardial hematoma also have been noted in single case reports.
For CCT images of post-infarction pseudoaneurysms, see Figure 20-4 .
True aneurysms of the LV most commonly are secondary to myocardial infarction but can (rarely) be congenital in origin or secondary to inflammatory (e.g., Kawasaki disease and sarcoidosis) or infectious (e.g., Chagas) disease. Occasionally changes associated with right ventricular dysplasia or hypertrophic cardiomyopathy also can be associated with LV aneurysm formation.