The incidence of pulmonary embolism in unexplained sudden cardiac arrest with pulseless electrical activity.

PURPOSE: The cause of many cases of sudden cardiac arrest from pulseless electrical activity is unknown. We hypothesized that pulmonary embolism was responsible for a substantial proportion of these cases and used transesophageal echocardiography to identify pulmonary embolism among patients with sudden cardiac arrest. SUBJECTS AND METHODS: We performed a prospective study at a tertiary care, university-operated county hospital, with a level 1 trauma center. Consecutive patients (n = 36) who were admitted with (n = 20) or unexpectedly developed (n = 16) sudden cardiac arrest of unknown cause were studied with transesophageal echocardiography during cardiopulmonary resuscitation. We determined the presence of central pulmonary embolism, right ventricular enlargement, and other causes of sudden cardiac arrest (such as myocardial infarction and aortic dissection) using prospectively defined criteria. RESULTS: Of the 25 patients with pulseless electrical activity as the initial event, 9 (36%) had pulmonary emboli (8 seen with transesophageal echocardiography and 1 diagnosed at autopsy) compared with none of the 11 patients with other rhythms, such as asystole or ventricular tachycardia or fibrillation (P = 0.02). Of the 8 patients who had pulmonary embolism diagnosed by transesophageal echocardiography, 2 survived to hospital discharge. CONCLUSIONS: Mortality from massive pulmonary embolism is high, particularly if patients present with sudden cardiac arrest. Earlier diagnosis of pulmonary embolus may permit wider use of thrombolytic agents or other interventions and may potentially increase survival.

Comparison of naive sixth-grade children with trained professionals in the use of an automated external defibrillator.

BACKGROUND: Survival after out-of-hospital cardiac arrest (OHCA) is strongly influenced by time to defibrillation. Wider availability of automated external defibrillators (AEDs) may decrease response times but only with increased lay use. Consequently, this study endeavored to improve our understanding of AED use in naive users by measuring times to shock and appropriateness of pad location. We chose sixth-grade students to simulate an extreme circumstance of unfamiliarity with the problem of OHCA and defibrillation. The children's AED use was then compared with that of professionals. METHODS AND RESULTS: With the use of a mock cardiac arrest scenario, AED use by 15 children was compared with that of 22 emergency medical technicians (EMTs) or paramedics. The primary end point was time from entry onto the cardiac arrest scene to delivery of the shock into simulated ventricular fibrillation. The secondary end point was appropriateness of pad placement. All subject performances were videotaped to assess safety of use and compliance with AED prompts to remain clear of the mannequin during shock delivery. Mean time to defibrillation was 90+/-14 seconds (range, 69 to 111 seconds) for the children and 67+/-10 seconds (range, 50 to 87 seconds) for the EMTs/paramedics (P<0.0001). Electrode pad placement was appropriate for all subjects. All remained clear of the "patient" during shock delivery. CONCLUSIONS: During mock cardiac arrest, the speed of AED use by untrained children is only modestly slower than that of professionals. The difference between the groups is surprisingly small, considering the naïveté of the children as untutored first-time users. These findings suggest that widespread use of AEDs will require only modest training.

Low yield of clinically significant transesophageal echocardiographic findings in patients with lacunar stroke.

Transesophageal echocardiography (TEE) is a sensitive technique for the detection of cardioembolic sources of stroke in patients with cryptogenic stroke. However, the yield of clinically significant TEE-detected abnormalities in other stroke subtypes such as lacunar stroke is unknown. We prospectively followed 145 consecutive stroke patients, including 26 patients with typical lacunar syndromes, to determine the relative risk of recurrent brain ischemia associated with TEE findings. The yield of TEE in patients with lacunar stroke syndromes was extremely low, except for a very high rate of atrial septal aneurysm (ASA). Although ASA was associated with a high risk of recurrent stroke or transient ischemic attack in patients with nonlacunar stroke, ASA was not associated with stroke recurrence in patients with lacunar stroke (p = 0.02, Cox's proportional hazard regression model). We conclude that TEE is unlikely to provide clinically relevant information in patients with typical lacunar syndromes.

Transesophageal echocardiography and carotid ultrasound in patients with cerebral ischemia: prevalence of findings and recurrent stroke risk.

OBJECTIVES: This study was conducted to determine the yield of transesophageal echocardiographic findings in a consecutive series of patients with stroke and transient ischemic attack, with and without carotid stenosis, and to estimate the recurrent stroke risk associated with specific echocardiographic findings. BACKGROUND: Transesophageal echocardiography has a high yield for identification of potential sources of cardiac embolism in patients with cerebral ischemia; however, the clinical significance of the most commonly detected abnormalities is uncertain. METHODS: We evaluated 145 consecutively admitted patients with stroke or transient ischemic attack with both transesophageal echocardiography and carotid ultrasound. Patients were followed up prospectively for a mean duration of 18 months to document the rate of recurrent cerebral ischemia. RESULTS: Transesophageal echocardiography detected at least one potential cardiac source of embolism in 45% of the patients. Atrial septal aneurysm and interatrial shunt were detected more frequently in patients who did not have a significant carotid stenosis that could account for their ischemic event. During follow-up, a higher rate of recurrent stroke or transient ischemic attack occurred in patients with positive transesophageal echocardiographic findings, particularly atrial septal aneurysm, interatrial shunt and left atrial thrombus. CONCLUSIONS: These data support recent studies that suggest that atrial septal aneurysm and interatrial shunts may be a significant source of cardioembolic stroke. Further studies are needed to clarify the optimal management of patients with these abnormalities.

Transesophageal echocardiographic findings in stroke subtypes.

BACKGROUND AND PURPOSE: Transesophageal echocardiography has a high yield for detecting potential cardiac sources of embolism in patients with clinical risk factors for cardioembolism or unexplained stroke. The yield in other stroke subtypes is unknown. METHODS: We classified 145 consecutively admitted patients into stroke subtypes based on clinical findings, brain imaging, and carotid ultrasound. Both transesophageal and transthoracic echocardiography were performed to detect left atrial thrombi, spontaneous echo contrast, atrial septal aneurysm, interatrial shunts, ventricular thrombus or aneurysm, and myxomatous mitral valve. RESULTS: Transesophageal echocardiography documented at least one of these findings in 46% of the patients compared with an 8% yield on the transthoracic study (P = .002). The yield of transesophageal echocardiography was substantial in all stroke subgroups. Patients with clinical risk factors for cardiac embolism had the highest frequency of spontaneous echo contrast (P = .001). Atrial septal aneurysms were most frequent in patients with lacunar syndromes (P = .012), and interatrial shunts were common in all stroke subtypes. CONCLUSIONS: Transesophageal echocardiographic findings vary considerably between stroke subgroups.

Transesophageal echocardiography in the evaluation of stroke.

OBJECTIVE: To review the current role of transesophageal echocardiography in the evaluation of stroke. DATA IDENTIFICATION: Articles examining the role of transesophageal echocardiography for evaluation of patients with stroke were identified using computer and bibliography searches. STUDY SELECTION: All English-language articles that provided full details on patient selection criteria, methods, and study design were reviewed. RESULTS OF DATA ANALYSIS: Cardiogenic embolism is frequently an uncertain diagnosis merely inferred by finding a potential cardiac source. Transthoracic echocardiography has had a low yield in screening unselected patients with stroke. Several series of patients with stroke have been reported comparing transthoracic and transesophageal echocardiography. Potential cardiac sources of embolism were consistently identified in many more patients by transesophageal echocardiography. Many findings are, however, of uncertain significance; these include spontaneous echo contrast, patent foramen ovale, filamentous strands on the mitral valve, and atrial septal aneurysm. CONCLUSIONS: Transesophageal echocardiography is most helpful in patients with stroke who are less than 45 years of age and in those without clinical evidence of heart disease. The indications for its use in the evaluation of stroke remain controversial. Further studies are needed using transesophageal echocardiography in patients with stroke and in control groups, not only to determine the natural history of transesophageal, echocardiographically detected abnormalities but also to evaluate treatment options.

Pseudocolor displays in B-mode imaging applied to echocardiography and vascular imaging: an update.

Cardiac and vascular ultrasound systems incorporting colorized gray-scale display options to supplement the standard B-mode gray-scale image have recently reappeared on the market from several manufacturers. As yet, the clinical benefit of this "new" technology is unknown, and recommendations and protocols for its best application are not available. This article reviews the limitations of the gray-scale displays currently used, the rationale of the color-supplemented B-mode image, and some of the potential applications to cardiac and vascular ultrasound.

Doppler echocardiography. Role in emergency diagnosis of cardiac valve disease.

Doppler echocardiography provides crucial information in the evaluation of a patient with suspected significant heart valve dysfunction. Doppler studies can provide quantitative data on the gradients across the stenotic valves and in many cases derive the actual valve area (with use of the pressure half-time method for stenotic atrioventricular valves or the continuity equation for semilunar valves). When combined with two-dimensional echocardiographic studies, Doppler studies may discern the cause of valve dysfunction. In valvular regurgitation, semi-quantitative estimation of the severity of the problem can be obtained by pulsed Doppler flow mapping or color Doppler echocardiography. These methods show great value for rapid evaluation of valve dysfunction in the emergency setting.

Diagnostic reliability of M-mode echocardiography for detecting mitral valve prolapse in 50 consecutive panic patients.

Fifty consecutive panic patients had M-mode echocardiographs read independently by two cardiologists with expertise in echocardiography. In this prospective study, there was poor interrater reliability (22 of 50; K = 0.11) for diagnosis of mitral valve prolapse (MVP). On repeat evaluation 10 months later there was also unacceptable intrarater reliability for each reader: 22 of 35 (K = 0.41) and 22 of 35 (K = 0.45). We conclude that M-mode echocardiography is clinically unreliable for establishing the diagnosis of mitral valve prolapse. These findings suggest that the variable reporting of M-mode-determined mitral valve prolapse in psychiatric populations may reflect differences among echocardiologists rather than differences in cardiac pathology. The clinical implications of these findings are discussed.

Left ventricular function during stable sustained ventricular tachycardia. Hemodynamic and echo-Doppler analysis.

To assess the left ventricular function during sustained stable ventricular tachycardia (VT), ten patients, aged 58 to 74, underwent simultaneous echo-Doppler and hemodynamic studies during sinus rhythm and induced sustained stable monomorphic VT. The VT cycle length was 447 +/- 92 ms (mean +/- SD). During VT, cardiac index fell from 2.32 +/- 0.54 to 1.62 +/- 0.63 L/min/m2 (p less than 0.001), and systemic systolic blood pressure fell from 129 +/- 18 to 107 +/- 18 mm Hg (p less than 0.001), while left ventricular end-diastolic pressure showed a rising trend from 9 +/- 7 to 15 +/- 12 mm Hg, and pulmonary artery wedge pressure rose from 10.2 +/- 1.6 to 24.2 +/- 2.3 mm Hg (p less than 0.005). By echo-Doppler the ejection fraction and the presence and degree of valvular regurgitation were not significantly changed during VT. The mean maximal left ventricular inflow tract velocities, mean time velocity integrals, and the mean time velocity integrals normalized for heart rate (measures of left ventricular diastolic filling) decreased from 0.59 +/- 0.074 to 0.40 +/- 0.053 m/s (p less than 0.05), from 0.12 +/- 0.029 to 0.021 +/- 0.012 m (p less than 0.001), and from 7.43 +/- 1.20 to 3.21 +/- 1.49 m x beats/min (p less than 0.001) during VT, respectively. We conclude that hemodynamic changes during stable sustained VT are neither associated with significant changes in systolic left ventricular function nor related to valvular regurgitation and are likely caused by impaired left ventricular diastolic filling.

Hypoxemia raises muscle sympathetic activity but not norepinephrine in resting humans.

The experimental objective was to determine whether moderate to severe hypoxemia increases skeletal muscle sympathetic nervous activity (MSNA) in resting humans without increasing venous plasma concentrations of norepinephrine (NE) and epinephrine (E). In nine healthy subjects (20-34 yr), we measured MSNA (peroneal nerve), venous plasma levels of NE and E, arterial blood pressure, heart rate, and end-tidal O2 and CO2 before (control) and during breathing of 1) 12% O2 for 20 min, 2) 10% O2 for 20 min, and 3) 8% O2 for 10 min--in random order. MSNA increased above control in five, six, and all nine subjects during 12, 10, and 8% O2, respectively (P less than 0.01), but only after delays of 12 (12% O2) and 4 min (8 and 10% O2). MSNA (total activity) rose 83 +/- 20, 260 +/- 146, and 298 +/- 109% (SE) above control by the final minute of breathing 12, 10, and 8% O2, respectively. NE did not rise above control at any level of hypoxemia; E rose slightly (P less than 0.05) at one time only with both 10 and 8% O2. Individual changes in MSNA during hypoxemia were unrelated to elevations in heart rate or decrements in blood pressure and end-tidal CO2--neither of which always fell. We conclude that in contrast to some other sympathoexcitatory stimuli such as exercise or cold stress, moderate to severe hypoxemia increases leg MSNA without raising plasma NE in resting humans.

Avoidance of retrograde catheterization by Doppler echocardiographic diagnosis of Björk-Shiley aortic valve dysfunction.

A 74-year-old man with a history of prior Björk-Shiley aortic valve replacement was admitted with chest pain and dyspnea. Results of physical examination and cinefluoroscopy suggested a dysfunction of the prosthetic valve; imaging echocardiography was not helpful. Nonimaging continuous wave Doppler examination confirmed severe prosthetic aortic valve dysfunction, necessitating emergent replacement, and potentially hazardous retrograde catheterization of the prosthesis was avoided.

Mitral valve prolapse and the anxiety disorders.

Confusing and contradictory results have emerged from studies of the relationship between anxiety disorders and mitral valve prolapse (MVP), a commonly occurring heart defect that has been associated with chest pain, palpitations, tachycardia, and arrhythmias. Patients with anxiety disorders, particularly panic attacks, appear to have an increased prevalence of MVP compared with control groups or the general population, although most individuals with MVP are asymptomatic. MVP does not appear to distinguish a subgroup of patients with panic disorder on the basis of vulnerability to panic attacks, symptom presentation, biological abnormalities, or treatment response. The authors review some current hypotheses about causal relationships between anxiety disorders and MVP, describe methods of diagnosing MVP and their shortcomings, and identify possible medical complications of MVP and ways to treat or prevent them.

Mitral valve abnormalities and catecholamine activity in anxious patients.

We studied 38 anxiety disorder patients, 19 of whom had evidence of mitral valve abnormalities by two-dimensional echocardiography. The presence or absence of mitral valve abnormalities was not related to 3-methoxy-4-hydroxyphenylglycol/creatinine excretion, platelet and plasma monoamine oxidase-type activity, or autonomic arousal as measured by blood pressure and resting heart rate. These findings fail to support the hypothesis that mitral valve abnormalities identify a specific subpopulation of anxious patients with differences in catecholamine function.

Differentiation of anxious patients by two-dimensional echocardiographic evaluation of the mitral valve.

Forty-four anxious patients with a history of panic attacks had a significantly higher prevalence of mitral valve abnormalities than 20 patients with generalized anxiety only. The higher number of mitral valve abnormalities was not correlated with the frequency of panic attacks.

Determination of the stenotic aortic valve area in adults using Doppler echocardiography.

The severity of aortic stenosis was evaluated by Doppler echocardiography in 48 adults (mean age 67 years) undergoing cardiac catheterization. Maximal Doppler systolic gradient correlated with peak to peak pressure gradient (r = 0.79, y = 0.63x + 25.2 mm Hg) and mean Doppler gradient correlated with mean pressure gradient (r = 0.77, y = 0.59x + 10.0 mm Hg) by manometry. The transvalvular pressure gradient is flow dependent, however, and associated left ventricular dysfunction was common in our patients (33%). Thus, of the 32 patients with an aortic valve area less than or equal to 1.0 cm2 at catheterization, 6 (19%) had a peak Doppler gradient less than 50 mm Hg. To take into account the influence of volume flow, aortic valve area was calculated as stroke volume, measured simultaneously by thermodilution, divided by the Doppler systolic velocity integral in the aortic jet. Aortic valve areas calculated by this method were compared with results at catheterization in the total group (r = 0.71). Significant aortic insufficiency was present in 71% of the population. In the subgroup without significant coexisting aortic insufficiency, closer agreement of valve area with catheterization was noted (n = 14, r = 0.91, y = 0.83x + 0.24 cm2). Transaortic stroke volume can be determined noninvasively by Doppler echocardiographic measures in the left ventricular outflow tract, just proximal to the stenotic valve. Aortic valve area can then be calculated as left ventricular outflow tract cross-sectional area times the systolic velocity integral of outflow tract flow, divided by the systolic velocity integral in the aortic jet.(ABSTRACT TRUNCATED AT 250 WORDS)