Sudden cardiac death in postmyocardial-infarction patients

Patients who survive a myocardial infarction are at increased risk for sudden death, owing largely to ventricular arrhythmia. In this article, we will review the epidemiology of sudden cardiac death in postmyocardial-infarction patients, arrhythmia mechanisms and substrate leading to cardiac arrest, identifying possible risk factors for sudden cardiac death (SCD) in high risk population and apply risk stratification strategies for prevention of SCD. We will also review relevant major trials and evidence-based therapy currently used, in addition to the indications and role of implantable cardioverter-defibrillators in this population. We will end this review with a summary of the current guidelines recommendations and a look into the future of this domain.

Superior vena caval syndrome: color flow Doppler detection of collateral venous channels

Thrombosis of the superior vena cava (SVC) is an important clinical problem that requires prompt diagnosis. Confirmation of suspected SVC syndrome requires the use of an imaging study to document the obstruction and presence of collateral venous channels. Echocardiography is often used to evaluate suspected SVC obstruction; however, previous methods have allowed only indirect detection of collateral flow. We describe 3 patients with SVC obstruction in whom color flow Doppler allowed direct demonstration of collateral venous channels.

Risk of dysphagia after transesophageal echocardiography during cardiac operations

BACKGROUND

Dysphagia can be a significant complication following cardiac operations. This study evaluates its incidence and relationship to intraoperative transesophageal echocardiography (TEE) for specific indications versus known factors such as stroke or prolonged intubation.

METHODS

Records of 838 consecutive cardiac surgical patients were reviewed, and categorized into those who received TEE for specific indications versus those who did not (nonTEE). Dysphagia was recorded when symptoms were confirmed by barium cineradiography. Multiple logistic regression identified significant factors causing dysphagia.

RESULTS

TEE was significantly related to the development of postoperative dysphagia by multiple logistic regression (p < 0.001). After controlling for other significant factors (stroke, left ventricular ejection fraction, intubation time, duration of operation), the odds of dysphagia for TEE patients was 7.8 times greater than for nonTEE patients.

CONCLUSIONS

TEE may be an independent risk factor for dysphagia following cardiac operations.

Echocardiography allows safer venous cannulation during excision of large right atrial masses

BACKGROUND

Excision of large right atrial masses requires bicaval cannulation and cardiopulmonary bypass. Safe venous cannulation can be accomplished only by knowing the exact intracavitary location and extension of the mass to avoid fragmentation. Transthoracic echocardiography and intraoperative transesophageal echocardiography, although helpful, cannot always define the exact intracavitary relationships of the tumor.

METHODS

We have used both intraoperative transesophageal and epicardial echocardiography to guide venous cannulation in 4 patients with large right atrial masses. Both echo images are used by the surgeon to select the exact site and method of cannulation to avoid fragmentation of the mass. Epicardial echocardiography complemented the images obtained by transesophageal echocardiography.

RESULTS

The technique of combined transesophageal and epicardial echocardiography allowed safe venous cannulation in all 4 patients. Each of the right atrial masses was safely excised using case-specific cannulation techniques guided by the echocardiographic images.

CONCLUSIONS

We propose the routine use of both intraoperative transesophageal and epicardial echocardiography in guiding venous cannulation for safe excision of large right atrial masses.

Aortic dissection in a neonate associated with arterial cannulation for extracorporeal life support

The purpose of this paper is to describe the authors' approach to the diagnosis and treatment of aortic intimal dissection encountered as a complication of the arterial cannulation procedure employed routinely during neonatal venoarterial ECMO. A case report is provided. Recognition of this entity clinically was based on diminished pulses in the lower extremities with dampening of an umbilical arterial catheter transduced pressure wave form one day after decannulation from ECMO. Confirmation was achieved using a phased array echocardiographic Doppler system (ECHO). Successful surgical repair was achieved under deep hypothermic circulatory arrest on cardiopulmonary bypass, with partial resection of the affected aorta, and with sutures placed through the intimal flap and the aortic wall. Aortic continuity was established by end-to-end anastamosis posteriorly, and the aortic arch was reconstructed anteriorly with an aortic homograft. To the author's knowledge, this is the first case of this problem being identified and treated in an ECMO treated neonate.

Aortic valvular disease in adults. A potentially lethal clinical problem

Patients who have asymptomatic aortic valvular disease with normal systolic ventricular function need careful follow-up, because both aortic stenosis and aortic regurgitation are potentially life-threatening. Medical therapy may be helpful for long-term management of patients with chronic aortic regurgitation, but valve replacement should be done before heart failure or refractory left ventricular dilatation develops. Aortic valve replacement is recommended in patients with symptomatic, severe aortic stenosis because of the high risk of sudden death if left untreated. Once valve replacement is indicated for either aortic stenosis or regurgitation, a choice must be made between a mechanical and a bioprosthetic valve, although allografts and autografts may become more widely used in the future.

Prognostic significance of ST-segment depression during adenosine perfusion imaging

To determine the significance of ST-segment depression during adenosine perfusion imaging for predicting future cardiac events, 188 patients with interpretable electrocardiograms were assessed 1 to 3 years (mean 21.5 +/- 6.6 months) after adenosine testing. At least 1 mm of ST-segment depression was observed in 32 (17%) patients, with > or = 2 mm of ST-segment depression in 10 (5.3%). Thirty-seven cardiac events occurred during the study period: 2 cardiac deaths, 5 nonfatal myocardial infarctions, 6 admissions for unstable angina, and 24 revascularizations. Univariate predictors of events were a history of congestive heart failure, previous non-Q-wave myocardial infarction, previous coronary angioplasty, use of antianginal medication, ST-segment depression during adenosine infusion (particularly > or = 2 mm), any reversible perfusion defect, transient left ventricular cavity dilation, and the severity of perfusion defects. Multivariate analysis identified > or = 2 mm ST-segment depression as the most significant predictor of cardiac events (relative risk [RR] = 6.5; p = 0.0001). Other independent predictors of events were left ventricular dilation (RR = 3.8; p = 0.002), previous coronary angioplasty (RR = 3.3; p = 0.001), a history of non-Q-wave myocardial infarction (RR = 2.3; p = 0.01), and the presence of any reversible defect (RR = 2.0; p = 0.05). We conclude that ST-segment depression occurs uncommonly during adenosine infusion, but the presence of > or = 2 mm of ST-segment depression is an independent predictor of future cardiac events and provides information in addition to that obtained from clinical variables and the results of adenosine perfusion imaging.

Mitral valve myxoma: a case report and brief review of the literature

A case of cardiac myxoma arising from the mitral valve is reported. A 50-year-old woman presented with history of shortness of breath and angina. Two-dimensional echocardiography showed a left atrial mass. At surgery, the tumor was found to be arising from the anterior leaflet of the mitral valve. The tumor was excised and a defect in the anterior leaflet of the mitral valve was repaired by direct suture.

False-positive reversible perfusion defect during dobutamine-thallium imaging in left bundle branch block

In the presence of pre-existing left bundle branch block (LBBB) exercise stress thallium scans have been associated with false-positive septal and apical perfusion abnormalities. Recent reports have documented a lower incidence of false-positive septal perfusion defects when pharmacologic agents such as dipyridamole or adenosine are utilized in patients with LBBB. Dobutamine, a synthetic catecholamine, is being used with increasing frequency in combination with perfusion agents for the diagnosis of coronary artery disease in patients unable to achieve an adequate exercise workload. Because the positive inotropic and chronotropic actions of doubtamine are similar to the physiologic effects of treadmill exercise, it is conceivable that false-positive perfusion abnormalities will be observed in patients with pre-existing LBBB undergoing dobutamine perfusion imaging. We describe a patient with underlying LBBB who underwent dobutamine thallium imaging which revealed septal and periapical defects. Subsequent coronary angiography showed these abnormalities to be false-positive. It is concluded that septal and periapical perfusion abnormalities during dobutamine thallium imaging may be false-positive and should be interpreted cautiously.

ST-segment depression during adenosine infusion as a predictor of myocardial ischemia

The incidence and hemodynamic changes associated with ST-segment depression during adenosine stress testing are poorly defined. To examine this, 550 consecutive patients who underwent adenosine perfusion testing were evaluated for the development of ST-segment depression. At least 1 mm of horizontal or downsloping depression developed in 82 patients (15.9%) and was observed with similar frequency in patients with normal scans and those with only fixed defects. ST depression developed in 58 of 242 patients with reversible defects (sensitivity = 24%) and in only 24 of 275 patients without reversible defects (specificity = 91%). Its presence was highly predictive of reversible perfusion defects (predictive accuracy = 71%). Similar findings were observed in patients with and without ECG evidence of left ventricular hypertrophy. Patients with ST depression had perfusion defects in more vessel distributions, had more severe defects, and had a greater increase in heart rate during adenosine infusion. Thus ST-segment depression occurs infrequently during adenosine infusion but is specific for and predictive of myocardial ischemia, as evidenced by reversible perfusion scan defects. Patients with ST depression have more severe disease and develop faster heart rates during infusion, which could result in decreased coronary perfusion during diastole allowing for the development of myocardial ischemia.