William Jacobs

Effect of Prone Positioning Systems on Hemodynamic and Cardiac Function During Lumbar Spine Surgery: An Echocardiographic Study

Study Design. Prospective randomized study of patients undergoing spine surgery. Objective. To compare changes in hemodynamic and cardiac function after prone positioning using different prone positioners. Summary of Background Data. Prone positioning decreases blood pressure and cardiac function. Several studies have evaluated changes in cardiac function after prone positioning, and linked them to reduced venous return and ventricular compliance. This study compares different prone positioners using transesophageal echocardiography, and determines their effect on cardiac function and hemodynamics. Methods. After correction of fluid deficits with the patient under stable anesthesia, hemodynamic and cardiac performance was measured using transesophageal echocardiography. After prone positioning, repeat measurements were performed, and comparisons were made between prone and supine positions. Results. No intergroup differences in demographics, fluid deficit, baseline hemodynamics, or differences from supine to prone position were noted. Cardiac output decreased with the Wilson (Union City, CA) and Siemens AG (Munich, Germany) frames, while cardiac index and stroke volume decreased with the Andrews (Hollywood, CA), Wilson, and Siemens systems. Cardiac preload decreased using the Andrews frame. The Jackson spine table (Hollywood, CA) and bolsters had the least effect on cardiac performance. Conclusion. Adequate fluid replacement reduced hypotension and hemodynamic instability after prone positioning. The Jackson spine table and longitudinal bolsters had minimal effects on cardiac function, and should be considered in patients with limited cardiac reserve.

Effect of an inelastic aortic synthetic vascular graft on exercise hemodynamics

This study compared aortic input impedance characteristics between patients with aortic interposition Dacron grafts placed for traumatic aortic injury and normal age-matched control subjects. All subjects were examined at rest and after treadmill exercise. Magnetic resonance imaging was conducted to rule out anatomic (stenosis) effects. Exercise increased characteristic impedance (ie, reduced aortic distensibility) by 29% and decreased total systemic arterial compliance by 21% in the patient group, whereas the normal control group showed insignificant change in these variables after exercise. Peripheral pressure wave reflection was reduced substantially with exercise (27%) in the control group, with much less reduction observed in the patient group. These abnormal vascular hemodynamics were associated with significantly high cardiac energetic costs in the patient group. A plausible explanation for the observed differences lies in the exaggerated vascular impedance mismatch between compliant aorta and inelastic graft, when cardiac output increases dramatically.

Transesophageal echocardiographic assessment of the contribution of intrinsic tissue thickness to the appearance of a thick mitral valve in patients with mitral valve prolapse.

OBJECTIVES This prospective, blinded transesophageal echocardiographic study was performed to determine the relative contributions of leaflet redundancy and overlap versus intrinsic tissue thickening as mechanisms for the apparent increase in diastolic thickness of the mitral valve. BACKGROUND Increased diastolic thickness of the mitral valve has been identified as an echocardiographic feature that predicts subsequent adverse sequelae in patients with mitral valve prolapse (MVP). METHODS Eleven patients with clinical and transthoracic echocardiographic evidence of MVP and 11 age-matched control subjects underwent protocol transesophageal echocardiography to image the mitral valve in two orthogonal planes and to measure its thickness in systole and diastole. RESULTS Maximal diastolic width of the slack, unloaded anterior leaflet was significantly greater in patients with MVP than in control subjects (mean +/- SD: 0.64 +/- 0.20 cm vs. 0.30 +/- 0.04 cm, p < 0.001). Similarly, diastolic posterior leaflet width was greater in patients with MVP (0.67 +/- 0.39 cm vs. 0.31 +/- 0.06 cm, p < 0.01). In contrast, minimal systolic width of the distended pressure-loaded mitral valve was not significantly different between patients with MVP and control subjects for either the anterior (0.22 +/- 0.05 cm vs. 0.20 +/- 0.04 cm, p = NS) or the posterior (0.25 +/- 0.07 cm vs. 0.24 +/- 0.05 cm, p = NS) leaflets. The percent change in leaflet width from diastole to systole (% delta W), an index of the contribution of dynamic factors (e.g., leaflet redundancy and overlap) to the apparent increase in diastolic leaflet thickness, was significantly greater in patients with MVP than in control subjects for both the anterior (% delta W 62 +/- 13% vs. 34 +/- 16%, p < 0.001) and the posterior (% delta W 54 +/- 19% vs. 22 +/- 21%, p < 0.005) leaflets. CONCLUSIONS The apparent increase in diastolic mitral leaflet thickness in patients with MVP versus control subjects is largely attributable to dynamic factors such as leaflet redundancy, overlap and deformation. During diastole, when the mitral leaflets are slack and unstressed, the leaflets appear markedly thickened in patients with MVP. In contrast, during systole, when developed intraventricular pressure distends the leaflets, causing them to stretch and balloon into the left atrium, the intrinsic tissue thickness is much less than that measured in diastole. These findings have important implications for the morphologic criteria used to diagnose MVP and the potential pathophysiologic mechanisms for adverse sequelae in this syndrome.

Arterial impedance in patients furing intraaortic balloon counterpulsation

BACKGROUND Symptomatic improvement of a patients hemodynamic condition during intraaortic balloon counterpulsation (IABC) is considered to result largely from a reduction in afterload. Afterload can be accurately quantified by arterial input impedance measurements. Here we report the effect of IABC on arterial impedance in humans. METHODS To characterize the effects of IABC on arterial input impedance, impedance measurements were obtained using aortic annulus Doppler flow and pressure from the aortic balloon catheter. Impedance spectra were compared between the cardiac cycles preceding and following the cycle with IABC in 25 patients. RESULTS Intraaortic balloon counterpulsation increased stroke volume (23%; p = 0.001), reduced myocardial oxygen demand (11%; p = 0.02), and decreased the aortic pressure at the onset of systole (16%; p = 0.001). There was also a decrease in systemic vascular resistance (24%; p = 0.001), characteristic arterial impedance (21%; p = 0.002), and pulse wave reflection (20%; p = 0.006). Linear regression analysis showed that an increase in stroke volume was predicted only by the decrease in systemic vascular resistance (r = -0.81; p = 0.001). CONCLUSIONS The reduction in systemic vascular resistance appeared to be the major mechanism by which IABC improved cardiac pumping efficiency. This effect may result from the passive distention of the peripheral vascular bed due to the propagation of the balloon-augmented diastolic pressure through the arterial system.

Heart transplantation in a patient with chloroquine-induced cardiomyopathy☆

We present the first report of a patient who underwent heart transplantation (HT) after endomyocardial biopsy (EMB) and revealed chloroquine-induced cardiomyopathy (CIC). This patient, who was treated with chloroquine for 6 years, developed a restrictive cardiomyopathy that progressed to congestive heart failure (CHF) resistant to medical management.

Ejection fraction: subjective visual echocardiographic estimation versus radionuclide angiography.

Objectives: The aim of this study was to validate the correlation of left ventricular ejection fraction (LVEF) between two‐dimensional (2D) echocardiography with harmonic imaging modality and radionuclide angiography (RNA) in a large number of patients. Background: Subjective visual estimation of LVEF is the most prevalent method in evaluating left ventricular systolic function. Previous published reports demonstrated that visual estimation from 2D was superior to other mathematical calculations, however the studies contained less than 50 patients. Methods: Retrospective review of 377 consecutive medical records containing LVEF from both 2D echocardiography and RNA obtained from the same patient within 15 days from January 1998 to September 1999. Results: Correlation coefficient value (r) between 2D echocardiography subjective visual estimation and RNA was 0.84. The r value was further increased to 0.87 when heart transplant recipients excluded. The agreement of LVEF between 2D echocardiography and RNA are higher in normal or severely depressed LV. Conclusion: Excellent correlation of LVEF exists between 2D echocardiography subjective visual estimation and RNA, especially in normal or severely depressed LV. (ECHOCARDIOGRAPHY, Volume 20, April 2003)

An unusual case of recurrent Loffler endomyocarditis of the aortic valve

Idiopathic hypereosinophilic syndrome is a rare systemic disease with an unexplained elevated eosinophil count. Loffler endomyocarditis is hypereosinophilic syndrome with endocardial fibrosis and restrictive cardiomyopathy. The atrioventricular valves are frequently involved, causing valvular regurgitation. Previously, there has been one case report of combined aortic and mitral valve involvement with Loffler endomyocarditis that was treated with bivalvular replacement. We describe a previously healthy 50-year-old man diagnosed with Loffler endomyocarditis complicated by peripheral thromboembolism and severe aortic regurgitation due to valve fibrosis and fibrotic vegetation on the aortic valve. He underwent embolectomy and aortic valve replacement in addition to treatment for his hypereosinophilia. He later presented with cardiomyopathy with severe aortic insufficiency due to the destruction of the aortic valve prosthesis by sterile fibrinous vegetation. To our knowledge, this is the second case in the literature in which Loffler endomyocarditis involves the aortic valve and the first patient in whom only the aortic valve is involved.

Infective aortic endocarditis after percutaneous balloon aortic valvuloplasty

Infective aortic endocarditis developed in an elderly patient after a percutaneous balloon aortic valvuloplasty. The transesophageal echocardiogram demonstrated a perivalvular abscess. The patient underwent surgical replacement of the infected valve, but later succumbed to renal failure. The development of infective aortic endocarditis should be recognized as a potentially fatal complication of percutaneous balloon aortic valvuloplasty. The important measures in preventing bacteremia during percutaneous balloon aortic valvuloplasty and the appropriate role of operation are discussed.

Hepatocellular carcinoma with intraatrial extension.

Neoplasms in the right atrium can be primary tumors, metastases, direct extensions from an adjacent organ, or extensions from the vena cava. We present the imaging of 3 cases of hepatoma with extension into the right atrium via the inferior vena cava (IVC). Although the diagnosis of myxoma was an early consideration in these patients, 2 of them were diagnosed as having hepatomas after further imaging studies prompted percutaneous biopsy. The diagnosis of hepatoma was not established in the third patient until the time of cardiac surgery. Our objective is to emphasize the importance of a thorough imaging evaluation in order to avoid unnecessary or inappropriate surgery when a patient is found to have an intraatrial mass.

A case of an isolated cleft in the posterior mitral leaflet

A 42-year-old woman complained of palpitation and chest discomfort. A mid-systolic click and faint systolic murmur were auscultated best at the apex. The transthoracic echocardiogram showed the presence of a cleft in the posterior mitral valve leaflet, along with posterior leaflet prolapse and mild mitral regurgitation (MR). The origin and direction of the MR jet suggest that the cleft is the mechanism of the regurgitation. No defect was noted in the anterior leaflet. An isolated cleft in the posterior mitral valve leaflet is an extremely rare congenital malformation, with only five cases being reported in the medical literature [1] (see Figs. 1, 2).