Paradoxical embolism as a cause of ischemic stroke of uncertain etiology. A transcranial Doppler sonographic study

A Unique Case of Inferior Vena Cava Aneurysm Complicated with Pulmonary Embolism and Cerebral Infarction

Inferior vena cava (IVC) aneurysms rarely occur. They are commonly detected incidentally since they present with mild or no symptoms. This was the first study to report a fatal case of a saccular IVC aneurysm with pulmonary embolism and cerebral infarction. The patient developed cardiac arrest five minutes after arriving at the emergency department, and spontaneous circulation was restored after two minutes of cardiopulmonary resuscitation. Computed tomography scans of the brain, chest, and abdomen–pelvis were obtained. The patient was diagnosed with a saccular aneurysm of the IVC measuring 8 × 11 cm, massive embolism of both pulmonary arteries, and cerebral infarction. An electroencephalogram, taken on the third day of hospitalization, suggested brain death, and the patient died on the eleventh day of hospitalization. This case report highlights that an IVC aneurysm with pulmonary embolism can be associated with paradoxical emboli-induced cerebral infarction, which is fatal.

Prevention of cardioembolic stroke

Cardiac causes of ischemic stroke lead to severe neurological deficits from large intracranial artery occlusion compared to small vessel ischemic stroke. The most common cause of cardioembolic stroke is atrial fibrillation (AF), which has an increasing incidence with age. AF stroke trials demonstrate that anti-coagulation is superior to anti-platelet therapy in terms of ischemic stroke prevention. Recently, warfarin was compared with dabigatran, an oral, direct thrombin inhibitor, and was found to be at least equally effective in reducing ischemic stroke with less intracranial bleeding risk. Future research is investigating other direct thrombin inhibitors as potential alternatives to warfarin, which has a narrow therapeutic index, requires frequent blood monitoring, has multiple drug interactions, and a higher rate of intracranial bleeding. Other causes of cardioembolic stroke include myocardial infarction, left ventricular thrombus, reduced ejection fraction, valvular abnormalities, and endocarditis. Patent foramen ovale is a common finding on echocardiograms in patients with and without stroke (up to 20% of the population), and it is a controversial source of cryptogenic stroke. The best way to prevent cardioembolic stroke remains early detection and treatment of AF, and treating the underlying stroke mechanism. Cardiac magnetic resonance imaging is an emerging technology and reveals some sources of cardiac embolism missed by echocardiography, and might provide an additional diagnostic tool in investigating cardioembolic stroke.

Cerebral emboli and paradoxical embolisation in dementia: a pilot study

BACKGROUND

The causes of the common dementias remain unknown. Paradoxical embolisation of the cerebral circulation by venous thrombi passing through venous to arterial shunts (v-aCS) in the heart or pulmonary circulation is known to occur in cryptogenic stroke and post-operative confusion following hip replacement.

OBJECTIVES

To explore the role of paradoxical embolisation in dementia by investigating for cerebral emboli, venous to arterial circulation shunt (v-aCS) and carotid artery disease.

METHODS

Forty-one patients with dementia (24 Alzheimer's AD and 17 vascular VaD) diagnosed using DSM-IV criteria and 16 controls underwent transcranial Doppler (TCD) detection of spontaneous cerebral emboli in both middle cerebral arteries. A v-aCS was detected by intravenous injection of an air/saline ultrasound contrast at rest and after provocation by coughing and Valsalva's manoeuvre. Carotid artery disease was assessed by duplex imaging.

RESULTS

Cerebral emboli were detected in 11 (27.5%) dementia patients compared with one (7%) control (p = 0.15) with emboli being most frequent in VaD (41%) compared to controls [OR (95% CI): 10.5 (1.1, 98.9), p = 0.04]. A v-aCS was detected in 25 (61%) patients and seven (44%) controls (p = 0.24). In dementia patients with cerebral emboli; v-aCS was detected in seven (64%) and moderate to severe carotid stenosis was present in three (30%).

CONCLUSION

Cerebral emboli and v-aCS may be more frequent in patients with both VaD and AD than in controls, which suggest paradoxical embolisation as a potential mechanism for cerebral damage. This pilot study justifies a definitive case-control study.

Prevalence of patent foramen ovale in subjects with obstructive sleep apnea: a transcranial Doppler ultrasound study

BACKGROUND

Under particular conditions a patent foramen ovale (PFO) can potentially give rise to ischemic stroke by means of paradoxic embolization. In obstructive sleep apnea syndrome (OSAS) right to left shunting (RLSh) can occur through PFO during periods of nocturnal apnea. Our study aimed to evaluate the prevalence of PFO diagnosed by means of transcranial Doppler (TcD) in subjects with OSAS.

METHODS

Seventy-eight consecutive subjects with OSAS (mean age 53+/-12 years) and 89 normal controls (mean age 48+/-9 years) underwent TcD with intravenous application of agitated physiological saline solution. The test was performed on patients at rest and during Valsalva maneuver.

RESULTS

PFO was present in 21 out of 78 patients with OSA (27%) and in 13 out of 89 control patients (15%). Seventeen out of 21 patients with OSA showed PFO only during Valsalva maneuver (85%) with respect to 12 out of 13 subjects of the control group (92%). Prevalence of PFO in OSAS was statistically different with respect to the control group (P<0.05). However, no statistically significant differences could be found for the prevalence of provocative-only shunting PFO with respect to already at rest shunting PFO in patients with OSAS with respect to the control group.

CONCLUSIONS

Prevalence of PFO in subjects with OSA is significantly higher than in normal controls. The shunt is frequently present only during Valsalva maneuver.

Suspected pulmonary embolism: enhancement of pulmonary arteries at deep-inspiration CT angiography--influence of patent foramen ovale and atrial-septal defect

PURPOSE

To investigate if abnormal early contrast enhancement of the aorta and decreased attenuation of pulmonary arteries at deep-inspiration spiral computed tomographic (CT) angiography might be caused by a patent foramen ovale (PFO).

MATERIALS AND METHODS

Two hundred forty-four spiral CT angiographic images of the pulmonary arteries obtained during deep inspiration in patients suspected of having pulmonary embolism (PE) were reviewed for evidence of abnormal early enhancement of the aorta. In 45 patients, enhancement of the ascending aorta was equal to or more than that of the pulmonary arteries. Nonenhanced or contrast material-enhanced echocardiography was performed in 39 of these cases. All CT images with abnormal enhancement patterns were graded for contrast quality with respect to sufficient enhancement of pulmonary arteries (four grades) at three anatomic levels: right and left main and lobar and segmental branches. In addition, all spiral CT angiographic images were evaluated concerning the diagnosis of PE and the grouping of central (main pulmonary artery to proximal lobar arteries) and peripheral (beyond proximal lobar branches) locations of emboli. Mean attenuation values of ascending aortas and main pulmonary arteries in group 1 (n = 244) were compared with those in groups 2 and 3 (n = 45) by means of the two-tailed Student t test for unpaired data (P <.05).

RESULTS

Attenuation values for ascending aortas in group 1 were significantly lower than those in groups 2 and 3 (P <.001). Attenuation values in main pulmonary arteries were significantly higher in group 1 than in groups 2 and 3 (P <.001). Echocardiographic images showed an intracardiac right-to-left shunt in all 39 cases with abnormal contrast dynamics in the CT study (16% of the whole study population). Three patients had an atrial-septal defect, and 36 had a PFO. Images with a shunt had good (9%), intermediate (37%), fair (33%), and poor (23%) contrast of the pulmonary arteries. Sufficient vessel contrast for the diagnosis of PE could not be achieved in 27 of 45 patients with a shunt, but severe central PE could be ruled out. PE could be diagnosed in 31% of the 244 images, 58% were negative, and 11% were indeterminate.

CONCLUSION

A PFO may frequently lead to insufficient attenuation of the pulmonary arteries, which potentially limits the diagnosis of PE if the examination is performed during deep inspiration.

Optimized transcranial Doppler technique for the diagnosis of cardiac right-to-left shunts

Transcranial Doppler sonography (TCD) is a simple method to detect a right-to-left cardiac shunt, although standardized procedures do not exist. In this study 69 patients were tested according to predetermined criteria and procedures (cluster of > 10 microbubbles, duration between injection in the cubital vein and detection in the middle cerebral artery [MCA] < or = 10 sec). Agitated saline solution was compared to oxypolygelatine, a plasma volume expander, as contrast media. Valsalva's maneuver and coughing were used to provoke right-to-left cardiac shunting, detected by TCD, transthoracic echocardiography (TTE), and transesophageal echocardiography (TEE). Oxypolygelatine caused a significantly higher number of microbubbles in the right atrium and MCA than did the saline solution, leading to a greater diagnostic reliability of TCD (paired t test, p < 0.001). Coughing did not provoke right-to-left cardiac shunts (x2 analysis, p < 0.001). The technique used for carrying out Valsalva's maneuver was important for the detection of right-to-left cardiac shunts. Twenty-five right-to-left shunts were diagnosed with TCD and 18 with TTE (36 vs 26%; x2 analysis, p = 0.1). The findings indicate that TCD when properly done is highly sensitive and specific for the diagnosis of right-to-left cardiac shunts.

Cerebral Embolism as a Cause of Stroke and Transient Ischemic Attack

The most frequent cause of stroke and transient ischemic attacks is cerebral embolism. Cardiogenic cerebral embolization is common among patients with any cause of atrial fibrillation (AF) but particularly in AF resulting from rheumatic and arteriosclerotic heart disease. Rare causes of cerebral embolism include fat entering the bloodstream after trauma, tumor cells arising from atrial myxomata, and gas embolism. Cerebral embolic infarctions and their sources of origin can now be confirmed during life by many invasive (I) and noninvasive (NI) procedures including computerized tomography (CT) scanning (NI), magnetic resonance imaging (MR) (NI), contrast angiography (I), digital subtraction angiography (I), magnetic resonance angiography (NI), carotid Doppler and transcranial Doppler (NI), and echocardiography (NI) without and with contrast. These tests visualize the following: embolic occlusions of small and large cerebral arteries, resultant cerebral infarctions in appropriate vascular territories, plaques within the aorta, subclavian, vertebral, and carotid arteries, and mural thrombi located within the heart and aortocephalic arteries. Transcranial Doppler monitoring of the middle cerebral artery detects both small (asymptomatic) and large (symptomatic) cerebral emboli, as well as transseptal cardiac shunting, which is a cause of paradoxical embolization. Holter monitoring detects episodic cardiac dysrhythmias not apparent during routine ECG. CT or MRI identify cerebral infarctions resulting from virtually all large cerebral emboli. Early recognition and identification of types of cerebral embolism are important because of the availability of effective prophylactic therapies. (ECHOCARDIOGRAPHY, Volume 13, September 1996)