Cardiac CT Imaging Is Key to Stroke Work-Up


CHICAGO — Up to 20% of strokes begin in the heart, so cardiac imaging should be part of the work-up of many stroke patients, Dr. Gautham Reddy said at the annual meeting of the American Society of Neuroradiology.

Electrocardiographically gated multidetector CT can assess the brain, cerebral vessels, and carotid arteries as well as the heart simultaneously and expedite diagnosis, he said.

At the University of California, San Francisco, where Dr. Reddy is chief of cardiac and pulmonary imaging, stroke patients are routinely scanned from the head down to the heart. Other modalities such as transthoracic or transesophageal echocardiography or MRI may be superior for evaluating cardiac masses, cardiomyopathy, or ischemic heart disease, but the ability to obtain a comprehensive evaluation from one sitting using CT can be advantageous for both the patient and physician—especially in the emergency setting.

The most common cardiac source of stroke is emboli, Dr. Reddy said. One such patient, diagnosed using multidetector CT, who had a history of atrial fibrillation and had been on anticoagulation, decided to stop taking his medication, then developed a stroke caused by a thrombus originating in the left atrium. Mitral stenosis is another common source of cardiac thrombus from the atrium.

Coagulation disorders and aneurysms may cause cardiac thrombi that originate in the ventricles. Left ventricular aneurysms may follow myocardial infarction and can be categorized as either true or false aneurysms.

True aneurysms characteristically have an anteroapical location with a wide ostium (greater than 50% of the aneurysm diameter). In contrast, false aneurysms are postdiaphragmatic with narrow ostia. Accurate and rapid diagnosis can have an impact on treatment, because true aneurysms are generally managed medically while false aneurysms require resection.

Cardiac tumors can also embolize to the brain. According to Dr. Reddy, about 98% of cardiac tumors are metastases from another source. Of primary cardiac tumors, myxomas, which are benign, are the most common and most likely to produce brain emboli. In fact, avoiding brain emboli is one of the major reasons for myxoma resection. Primary malignant tumors of the heart, such as angiosarcomas, also have the potential to embolize and cause stroke, as can secondary tumors such as lymphoma.

Cardiac imaging also can reveal the presence of patent foramen ovale or other septal defects in patients with strokes. These openings allow a clot or tumor to pass from the right side to the left side of the heart, and then enter the arterial circulation as a paradoxical embolism. Repair of even small defects may be recommended to avoid subsequent strokes, Dr. Reddy said.

Reconstructed coronal imaging shows a thrombus in the left atrial appendage.

The arrow shows a thrombus in a true aneurysm of the left ventricle.

A false aneurysm in the postero-inferior aspect of the LV is reconstructed on CT. Photos courtesy Dr. Gautham Reddy

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