Comparative efficacy of three indexes of left ventricular performance derived from pressure-volume loops in heart failure induced by tachypacing.

OBJECTIVES: The purpose of this study was to serially evaluate the response and variability of the end-systolic pressure-volume relation, the left ventricular end-diastolic volume-peak positive first derivative of left ventricular pressure (dP/dt) relation and the left ventricular end-diastolic volume-stroke work relation in the development of progressive left ventricular dysfunction. BACKGROUND: Evaluation of systolic performance of the failing left ventricle may be enhanced by using relatively load-insensitive measures of left ventricular performance. The end-systolic pressure-volume, left ventricular end-diastolic volume-peak positive dP/dt and left ventricular end-diastolic volume-stroke work relations adequately define left ventricular performance under multiple loading conditions, but efficacy has not been fully assessed in the failing heart, particularly in the intact circulation. METHODS: Fourteen dogs underwent instrumentation and rapid pacing to heart failure. Variably loaded pressure-volume beats were produced by inferior vena cava occlusion. The dogs were evaluated at baseline and at three progressively more severe levels of left ventricular dysfunction. RESULTS: There was a progressive increase in left ventricular volumes at end-diastole ([mean value +/- SE] 60 +/- 28 to 73 +/- 29 ml, p < 0.001) and end-systole (39 +/- 19 to 61 +/- 27 ml, p < 0.001) during the 3 weeks of rapid pacing and a progressive decline in peak positive dP/dt (1,631 +/- 410 to 993 +/- 222 mm Hg/s, p < 0.001) and ejection fraction (37 +/- 8% to 16 +/- 11%, p < 0.001). There was a corresponding decline in the slope of each of the three relations: for end-systolic pressure-volume, 6.3 +/- 2.2 to 2.8 +/- 0.7 (p < 0.05); for left ventricular end-diastolic volume-stroke work, 61.9 +/- 9.1 to 26.5 +/- 2.4 (p < 0.05); and for left ventricular end-diastolic volume-peak positive dP/dt, 47.1 +/- 13.6 to 20.31 +/- 6.8 (p < 0.05). There was also a corresponding increase in position volumes: for end-systolic pressure-volume, 33.6 +/- 3.9 to 61.2 +/- 6.6 ml (p < 0.05); for left ventricular end-diastolic volume-stroke work, 46.2 +/- 3.6 to 89.3 +/- 7.6 ml (p < 0.05); and for left ventricular end-diastolic volume-peak positive dP/dt, 29.1 +/- 19.1 to 68.6 +/- 25.9 ml (p < 0.05). The relative degree of change in each of the three relations was similar as more severe heart failure developed. The coefficients of variation for position were significantly less than the variation for slopes. The response of volume intercepts was heterogeneous. For left ventricular end-diastolic volume-stroke work, the intercept increased as ventricular performance decreased. The intercept of the end-systolic pressure-volume relation was significantly more variable than the left ventricular end-diastolic volume-stroke work relation and did not change with progressive heart failure. The intercept for left ventricular end-diastolic volume-peak positive dP/dt was highly variable and showed no consistent changes as left ventricular function declined. CONCLUSIONS: All three relations consistently describe changes in left ventricular performance brought about by tachypacing. Evolution of left ventricular dysfunction causes a decline in slope and a rightward shift of these relations. The position of the relation is the most sensitive and least variable indicator of left ventricular systolic performance.

Successful reversal by chelation therapy of congestive cardiomyopathy due to iron overload.

A patient who developed severe iron overload cardiomyopathy is described. Venesection could not be performed because the patient had chronic anemia. Deferoxamine mesylate, a chelating agent, was administered daily for more than 2 years and produced significant improvement in ventricular function which was associated with a biopsy-proven decrease in myocardial iron stores. This is the first reported case in which a severe cardiomyopathy due to iron overload was reversed by chelation therapy alone.

Reversed closure sequence of the mitral and tricuspid valves in congestive heart failure.

OBJECTIVES: The purpose of this study was to evaluate functional and hemodynamic factors that determine the mitral-tricuspid and aortic-pulmonary valve closure sequence in patients with dilated cardiomyopathy. BACKGROUND: The physiologic factors determining closure sequence of cardiac valves in various forms of heart disease have been found to be complex. Few data exist for dilated cardiomyopathy, particularly for differentiating the effects of a conduction delay versus changes in ventricular performance. METHODS: A group of 64 patients were compared with 36 control subjects. Timing of valve closure and electromechanical intervals were determined by combined M-mode echocardiography, phonocardiography and apexcardiography. Hemodynamic data from right heart catheterization were available in 46 patients. RESULTS: In all control subjects, the aortic valve closed before the pulmonary valve and the mitral valve closed before the tricuspid valve. In the study group, 30 patients (49%) had reversed aortic-pulmonary valve closure and 27 (90%) of these had a left-sided conduction delay. There were 38 patients (60%) who had reversed mitral-tricuspid valve closure, but this was unrelated to the presence of a left-sided conduction delay. The presence of high ventricular filling pressures and poor systolic function was associated with delayed closure of both the mitral and the tricuspid valve. This caused the closure sequence to be related to the size of the difference between mean pulmonary artery wedge pressure and mean central venous pressure and also the magnitude of right ventricular dysfunction. Patients with a low wedge pressure (< 16 mm Hg) and a low central venous pressure (< 10 mm Hg) had a low prevalence of mitral-tricuspid valve closure reversal (30%). Those with a high wedge pressure (> 16 mm Hg) but a low central venous pressure had a high prevalence (86%) of reversal of mitral-tricuspid valve closure. Patients with high wedge and central venous pressures had a moderate prevalence (47%) of mitral-tricuspid valve closure reversal. Similar findings were observed for right ventricular dysfunction. If the right ventricle was normal or severely dysfunctional, a reversed closure sequence was less common (52% and 41%, respectively) than if moderate dysfunction was present (78%). CONCLUSIONS: Aortic-pulmonary valve closure sequence is strongly related to the presence of a left-sided conduction delay. The mitral-tricuspid valve closure sequence is unrelated to a conduction delay but can be reversed by relative differences in the severity of systolic dysfunction and filling pressures between the two ventricles.

Low-dose enoximone improves exercise capacity in chronic heart failure. Enoximone Study Group.

OBJECTIVES: This study was designed to evaluate the effects of low-dose enoximone on exercise capacity. BACKGROUND: At higher doses the phosphodiesterase inhibitor, enoximone, has been shown to increase exercise capacity and decrease symptoms in heart failure patients but also to increase mortality. The effects of lower doses of enoximone on exercise capacity and adverse events have not been evaluated. METHODS: This is a prospective, double-blind, placebo-controlled, multicenter trial (nine U.S. centers) conducted in 105 patients with New York Heart Association class II to III, ischemic or nonischemic chronic heart failure (CHF). Patients were randomized to placebo or enoximone at 25 or 50 mg orally three times a day. Treadmill maximal exercise testing was done at baseline and after 4, 8 and 12 weeks of treatment, using a modified Naughton protocol. Patients were also evaluated for changes in quality of life and for increased arrhythmias by Holter monitoring. RESULTS: By the protocol-specified method of statistical analysis (the last observation carried-forward method), enoximone at 50 mg three times a day improved exercise capacity by 117 s at 12 weeks (p = 0.003). Enoximone at 25 mg three times a day also improved exercise capacity at 12 weeks by 115 s (p = 0.013). No increases in ventricular arrhythmias were noted. There were four deaths in the placebo group and 2 and 0 deaths in the enoximone 25 mg three times a day and enoximone 50 mg three times a day groups, respectively. Effects on degree of dyspnea and patient and physician assessments of clinical status favored the enoximone groups. CONCLUSIONS: Twelve weeks of treatment with low-dose enoximone improves exercise capacity in patients with CHF, without increasing adverse events.

The electrocardiogram in systemic sclerosis (scleroderma). Study of 102 consecutive cases with functional correlations and review of the literature.

The electrocardiographic findings in 102 consecutive patients with scleroderma were reviewed to determine the frequency and nature of the electrocardiographic abnormalities associated with this disease. Septal infarction pattern unassociated with QRS prolongation was present in 10 percent, compared with none of 96 control subjects (p less than 0.001). Ventricular conduction abnormalities were present in 17 percent. A normal electrocardiogram was obtained in 49 percent. A subset of 48 patients underwent detailed cardiopulmonary evaluation including exercise thallium scintigraphy, rest and exercise radionuclide ventriculography, pulmonary function tests, and chest roentgenography. Functional correlations of the electrocardiographic findings were examined in this subset. Septal infarction pattern (five of 48) and ventricular conduction abnormalities (10 of 48) were both associated with septal or anteroseptal thallium perfusion abnormalities (10 of 15 versus six of 33 of the remainder, p less than 0.005), which were present despite normal coronary angiographic results. Thallium defect scores were greater in patients with septal infarction pattern or ventricular conduction abnormalities compared with the remainder (defect scores 3.0 +/- 2.6 versus 1.4 +/- 2.2, respectively, p less than 0.025). In patients with ventricular conduction abnormalities, both left bundle branch block and right bundle branch block with left anterior fascicular block were associated with abnormal left ventricular function, whereas isolated right bundle branch block or left anterior fascicular block was associated with normal left ventricular function. A normal electrocardiographic finding (19 of 48) was associated with normal left ventricular function at rest (19 of 19). However, 11 of 19 (58 percent) had thallium perfusion defects and four of 19 (21 percent) had an abnormal response to exercise, although in none was the peak ejection fraction less than 50 percent. It is concluded that both septal infarction pattern and ventricular conduction abnormalities are electrocardiographic abnormalities associated with scleroderma heart disease; they appear to be a result of myocardial fibrosis. Some degree of myocardial fibrosis may be present with a normal electrocardiographic result, but significant left ventricular dysfunction is unlikely. Septal infarction pattern and ventricular conduction abnormalities, when present, are indicators of more advanced fibrosis.

Noninvasive evaluation of systolic and diastolic function in severe congestive heart failure secondary to coronary artery disease or idiopathic dilated cardiomyopathy.

The usefulness of systolic time intervals, diastolic time intervals and echocardiography in evaluating left ventricular (LV) function was determined in 69 patients with severe congestive heart failure. All systolic time intervals were markedly abnormal (preejection period/LV ejection time 0.59 +/- 0.18 vs 0.30 +/- 0.04, preejection period index 170 +/- 37 vs 117 +/- 11, LV ejection time index 372 +/- 26 vs 410 +/- 17; patients vs control subjects, p less than 0.05). Diastolic time intervals in patients were not different from those in control subjects. Echocardiographic measurements were all markedly abnormal (LV end-diastolic dimension 6.9 +/- 1.0 vs 4.8 +/- 0.4 cm, patients vs control subjects, p less than 0.05). No pattern of abnormalities distinguished ischemic cardiomyopathies from idiopathic dilated cardiomyopathies. The presence of LV conduction delay did not substantially alter results, except that exclusion of patients with LV conduction delay normalized the total time of systole (QA2) index (from 542 +/- 40 to 531 +/- 31 ms) and reduced but did not normalize prolongation in the preejection period index (from 170 +/- 37 to 162 +/- 29 ms). No systolic or diastolic interval strongly correlated with any hemodynamic or other independent measure of LV performance. Twenty-four patients were given inotropic or unloading agents, which significantly improved hemodynamic values. Systolic and diastolic intervals were measured at baseline and at maximal hemodynamic effect. The correlation of changes in hemodynamics with changes in systolic and diastolic intervals was only modest. Thus, although systolic time intervals and associated echocardiographic measurements can detect abnormal LV function, they cannot reliably detect a change in LV function or distinguish gradations of abnormality.(ABSTRACT TRUNCATED AT 250 WORDS)

Extent of mitral calcific deposits determined by cineangiography in mitral stenosis and their effect on valve motion, hemodynamics and clinical signs.

The relation between the degree of leaflet calcium in a stenotic mitral valve and several parameters of valve mobility, hemodynamics and clinical signs was determined in 105 patients with relatively pure mitral stenosis (MS). The amount of mitral valve calcific deposits was determined by grading cineangiograms. Compared to 71 patients with no or minimal valvular calcium, the 23 patients with heavy valve leaflet calcium were significantly older, more likely to be men and more likely to be in atrial fibrillation. These patients also had a significant reduction of valve mobility in that their M-mode measurements of valve excursion and rate of valve opening were significantly reduced compared to those of patients without heavy valvular calcium. Two-dimensional echocardiograms also documented a significant reduction in valve mobility and progressive restriction in doming of the anterior mitral leaflet as the level of calcium increased. The prevalence of an opening snap was significantly decreased in patients with heavy vs no or light valvular calcium, and patients without an opening snap had reduced valve mobility. However, a considerable number of patients with moderate to heavy valve calcium retained an opening snap.

Echophonocardiographic estimates of pulmonary artery wedge pressure in mitral stenosis.

The efficacy of noninvasive indexes for predicting pulmonary artery wedge (PAW) pressure was reviewed in 77 patients with mitral stenosis. M-mode echocardiography and phonocardiography were used to measure the aortic valve closure-mitral valve E-point interval (A2-E) and the electrocardiographic Q wave-mitral valve closure interval (Q-C) close to the time of diagnostic cardiac catheterization. During catheterization, in 65 patients PAW pressure was measured and in 12 left atrial (LA) pressure was measured. The A2-E and Q-C intervals taken alone had only modest correlation with PAW pressure (r = -0.54 and r = 0.46, respectively). The correlation was weakest in patients with atrial fibrillation and best in sinus rhythm when heart rate variation between invasive and noninvasive studies was within +/- 5 beats. Substitution of V-wave pressure for mean PAW pressure and correction for variation in blood pressure improved the A2-E correlation (r = -0.64), as did combining the A2-E and Q-C intervals into a ratio [(Q-C)/(A2-E)] (r = 0.62). However, the best results were obtained in patients where LA pressure was measured directly (r = -0.91 for A2-E), suggesting the PAW pressure is not always an accurate reflection of LA pressure. In conclusion, many factors in addition to LA pressure affect the Q-C and A2-E intervals which, in many situations, decrease their predictive value. However, if used appropriately, these intervals may allow an estimation of PAW pressure.

Safety, tolerance, and efficacy of adenosine as an additive to blood cardioplegia in humans during coronary artery bypass surgery.

Myocardial stunning after heart surgery is associated with increased morbidity and mortality in patients with severe multivessel disease and reduced myocardial function. The purpose of this study was to evaluate the safety, tolerance, and efficacy of adenosine as a cardioprotective agent when added to blood cardioplegia in patients undergoing coronary artery bypass surgery. Sixty-one patients were randomized to standard cold-blood cardioplegia, or cold-blood cardioplegia containing 1 of 5 adenosine doses (100 microM, 500 microM, 1 mM, 2 mM, and 2 mM with a preischemic infusion of 140 microg/kg/min of adenosine). Invasive and noninvasive measurements of ventricular performance and rhythm were obtained preoperatively, prebypass, and then at 1, 2, 4, 8, 16, and 24 hours postbypass. Use of inotropic agents and vasoactive drugs pastoperatively was recorded; blood samples were collected for measurement of nucleoside levels. High-dose adenosine treatment was associated with a 249-fold increase in the plasma adenosine concentration and a 69-fold increase in the combined levels of adenosine, inosine, and hypoxanthine (p <0.05). Increasing doses of the adenosine additive were also associated with lower requirements of dopamine (p = 0.003) and nitroglycerine (p = 0.001). The 24-hour average doses for dopamine and nitroglycerine in the placebo group were 28-fold and 2.6-fold greater than their respective high-dose adenosine treatment cohorts. Finally, the placebo- and 100 microM-adenosine group was associated with a lower ejection fraction when compared to patients receiving the intermediate dose or high-dose treatment. These findings are consistent with the hypothesis that adenosine is effective in attenuating myocardial stunning in humans.

Infiltration of a cerebral artery aneurysm by malignant lymphoma cells with acute rupture: Report of a case.

A 55 year old woman died suddenly of a ruptured cerebral artery aneurysm. The aneurysm. was infiltrated by cells from a silent, nodular, poorly differentiated lymphocytic lymphoma, which also involved the spleen and abdominal lymph nodes. Compared to leukemias, the incidence of cerebral hemorrhage in non-Hodgkin's lymphomas is exceedingly rare, this being the first case reported in detail. A brief discussion of the etiology of cerebral hemorrhage in lymphomas is provided.

High-voltage injury resulting in permanent right heart dysfunction.

This report describes the case of a 27-year-old man who survived a high-voltage chest injury that resulted in acute biventricular dysfunction. Although the prognosis is generally poor, complete recovery of cardiac function over days to weeks has been documented. This case is unique because the patient regained complete recovery of left ventricular function over 3 months, but had persistent right heart dysfunction on serial echocardiographic evaluations.

Pericardial cyst with partial erosion of the right ventricular wall.

A case of pericardial cyst with partial erosion into the anterior wall of the right ventricle is presented. Cardiopulmonary bypass was necessary for excision of the cyst. This report helps to alert surgeons of the possible need for cardiopulmonary bypass during the removal of some pericardial cysts, especially in patients with signs and symptoms of infection and in whom preoperative imaging fails to show distinct margins between the cyst and cardiac structures.

Doppler characteristics of late-diastolic flow in the left ventricular outflow tract.

This study characterizes the relationship between late-diastolic Doppler detected forward flow in the left ventricular outflow tract and diastolic transmitral flow. Pulsed-wave Doppler interrogation of the left ventricular outflow tract, in a prospective consecutive series (n = 137), revealed the presence of end-diastolic forward flow in 83% of the patients studied. Further quantification of both flow signals was performed in 67 patients. Pulsed-wave mapping demonstrated that peak velocity of the end-diastolic left ventricular outflow tract signal (J wave) was maximal, 2.6 +/- 0.7 cm from the aortic valve anulus, and occurred 48 +/- 34 milliseconds after the peak transmitral atrial velocity flow signal. Peak J velocity ranged from 25 to 118 cm per second and correlated with peak A velocity (r = 0.69, p less than 0.001). Peak J velocity was inversely related to left ventricular end-diastolic dimension (r = -0.53, p less than 0.0001) and left ventricular end-diastolic volume (r = -0.43, p less than 0.004). There was no relationship between J wave velocity and early diastolic filling. We concluded that a late-diastolic forward flow signal is commonly observed in the left ventricular outflow tract. It is a manifestation of transmitral atrial systolic flow in the left ventricular outflow tract and is determined predominantly by peak transmitral atrial velocity and left ventricular size.

Improved echocardiographic detection and characterization of left ventricular apical thrombi with a 5.0 MHz short-focus transducer.

Transthoracic echocardiography is a frequently used technique for detecting ventricular thrombi. This study compares the usefulness of a 5.0 MHz short focal length transducer (5-short) with standard frequency (2.5 or 3.5 MHz) transducers for the detection of left ventricular thrombi. In addition, the effect of body habitus on study quality was evaluated. A consecutive series of 101 patients sent for echocardiographic imaging with the diagnosis of myocardial infarction, dilated cardiomyopathy, or recent suspected embolic event were imaged in the apical four-chamber, apical long-axis, and apical two-chamber views with a standard transducer and also with the 5-short. Out of this group, 16 apical thrombi were identified, six with the 5-short only, three with standard transducers only, and seven by both techniques. The areas of the seven thrombi detected by both transducers were consistently larger when measured on 5-short images compared with standard transducer images (4.6 +/- 2.3 vs 3.7 +/- 2.3 cm2, p = 0.02). In the three studies positive only with the standard transducers, the 5-short demonstrated only prominent trabeculae but no thrombus. The studies positive only with the 5-short had significantly smaller calculated thrombi areas than those visualized by the standard transducers (1.6 +/- 1.2 vs 4.2 +/- 2.1 cm2, p = 0.02). No thrombus was detected by either technique in a normally contracting left ventricular apex. There were significantly fewer studies having near-field artifact when performed by the 5-short compared with those performed with standard transducers (14/101 vs 40/101, p = 0.00004).(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical utility of automatic boundary detection for the determination of left ventricular volume: a comparison with conventional off-line echocardiographic quantification.

The aim of this study was to compare measurements of echocardiographic volume with an on-line automatic boundary detection imaging system with those of a conventional off-line method for routine clinical studies. Automatic boundary detection imaging shows promise as a rapid, on-line method for quantitating left ventricular volumes by echocardiography. However, there is little information about the role of automatic boundary detection for routine clinical studies. Ninety-seven patients with a variety of clinical diseases who were referred for clinical transthoracic echocardiographic evaluation were studied in apical four-chamber and two-chamber imaging planes. End-diastolic volume, end-systolic volume, and ejection fraction obtained with automatic boundary detection images were compared with those of conventional off-line analysis. Segmental endocardial definition and border tracking were evaluated on all automatic boundary detection images. Left ventricular end-diastolic volumes obtained by automatic boundary detection correlated well but were systematically under-estimated compared with off-line analysis for the apical two-chamber (r = 0.83; underestimation = 42 +/- 33 ml; p < 0.05) and four-chamber views (r = 0.83; underestimation = 43 +/- 31 ml; p < 0.05). Left ventricular end-systolic volumes also correlated well but were underestimated by automatic boundary detection for the apical two-chamber (r = 0.83; underestimation = 14 +/- 26 ml; p < 0.05) and four-chamber views (r = 0.83; underestimation = 18 +/- 24 ml; p < 0.05). Ejection fraction was not predicted accurately for the entire study population (n = 97). However, for patients with complete endocardial definition (n = 32), automatic boundary detection accurately predicted ejection fraction with no systematic error compared with manually traced images for both the apical two-chamber (r = 0.86; p < 0.05) and four-chamber (r = 0.82; p < 0.05) views. Segmental analysis of endocardial tracking revealed significantly better tracking of the septal and lateral walls compared with other regions (p < 0.05). End-diastolic and end-systolic volumes determined by automatic boundary detection correlate well but underestimate volume compared with conventional off-line analysis. However, ejection fraction compares favorably for the two methods when there is complete endocardial definition.

Reliability of M-mode, two-dimensional and Doppler echocardiography in diagnosing a flail mitral valve leaflet.

The purpose of this study was to evaluate the M-mode, two-dimensional, and Doppler echocardiographic signs for a flail mitral valve leaflet. This was a retrospective evaluation of 54 patients who had (1) significant mitral regurgitation, (2) a technically adequate echocardiographic study, and (3) description of valve anatomy done at surgery or necropsy. The following M-mode signs were examined for their ability to detect a flail valve: (1) systolic flutter of the mitral valve closure line, sensitivity 29%, specificity 76%; (2) abnormal diastolic posterior leaflet motion, sensitivity 73%, specificity 71%; (3) abnormal diastolic anterior leaflet motion, sensitivity 67%, specificity 86%; (4) systolic atrial echoes, sensitivity 28%, specificity 68%; (5) multiple independent systolic closure lines, sensitivity 71%, specificity 52%. The two-dimensional echocardiographic signs evaluated were (1) diastolic inversion of the anterior leaflet toward the left atrium, sensitivity 29%, specificity 96%; (2) diastolic inversion of the posterior leaflet toward the left atrium, sensitivity 54%, specificity 93%, (3) systolic inversion of the anterior leaflet into the left atrium, sensitivity 57%, specificity 93%; (4) systolic inversion of the posterior leaflet into the left atrium, sensitivity 79%, specificity 86%; (5) systolic whipping of the mitral leaflets, sensitivity 73%, specificity 74%; (6) presence of floating apical chordae, sensitivity 30%, specificity 91%. Doppler echocardiographic signs evaluated were (1) presence of left atrial systolic antegrade flow, sensitivity 30%, specificity 91%; (2) vertical striations superimposed on the typical regurgitant flow pattern, sensitivity 75%, specificity 69%. When all the two-dimensional signs except systolic whipping and the M-mode signs for abnormal diastolic leaflet motion were combined, the sensitivity for detecting a flail mitral valve was maximized at 97%, but specificity was reduced to 64%. In conclusion, two-dimensional echocardiographic signs are more sensitive and specific than either M-mode or Doppler signs for detecting a flail mitral valve. The various M-mode, two-dimensional, and Doppler echocardiographic signs, however, are complementary to each other, and sensitivity is maximized when they are combined.

Surgical resection of cor triatriatum in a 74-year-old man. Review of echocardiographic findings with emphasis on Doppler and transesophageal echocardiography.

A 74-year-old man was admitted to the hospital with congestive heart failure secondary to cor triatriatum. He also had sick sinus syndrome with complete heart block and syncope that had been treated with a permanent pacemaker 20 years earlier. The patient underwent successful surgical resection of the atrial membrane with closure of an atrial septal defect. M-mode, two-dimensional, Doppler, and transesophageal echocardiographic findings are reviewed. A unique "spike and dome" pattern on continuous-wave Doppler echocardiography is described that may suggest diagnosis of cor triatriatum.

Transesophageal echocardiography for the evaluation and management of patients with cerebral ischemia.

To prevent recurrent strokes and transient ischemic attacks, considerable attention is devoted to investigating the etiology of acute cerebral ischemia in the large subpopulation of patients without an easily identifiable cause. In general, transthoracic echocardiography is an insensitive tool for the evaluation of patients with cerebral ischemia, unless clinical signs and/or symptoms of cardiac disease are present. Transesophageal echocardiography (TEE), because of its increased sensitivity for aortic arch atheromata, atrial septal pathology, left atrial thrombi, and valvular abnormalities, is the preferred cardiac imaging modality, especially in young patients, older patients with hypertension or systemic atherosclerosis, and patients with prosthetic heart valves. This paper reviews the prognostic and therapeutic impact of TEE in patients with cerebral ischemia, specifically focusing on the ability of information obtained by this technique to alter patient management and improve risk stratification.

Estimating the probability that the Taser directly causes human ventricular fibrillation.

This paper describes the first methodology and results for estimating the order of probability for Tasers directly causing human ventricular fibrillation (VF). The probability of an X26 Taser causing human VF was estimated using: (1) current density near the human heart estimated by using 3D finite-element (FE) models; (2) prior data of the maximum dart-to-heart distances that caused VF in pigs; (3) minimum skin-to-heart distances measured in erect humans by echocardiography; and (4) dart landing distribution estimated from police reports. The estimated mean probability of human VF was 0.001 for data from a pig having a chest wall resected to the ribs and 0.000006 for data from a pig with no resection when inserting a blunt probe. The VF probability for a given dart location decreased with the dart-to-heart horizontal distance (radius) on the skin surface.