Biomedical subjects

James D Thomas

Publications and source records attributed to James D Thomas.

At least 109 records · Page 6Linked to original sources

PubMed2003

Pulmonary venous flow by doppler echocardiography: revisited 12 years later.

In 2003, pulmonary venous flow (PVF) evaluation by Doppler echocardiography is being used daily in clinical practice. Twelve years ago, we reviewed the potential uses of PVF in various conditions. Some of its important uses in cardiology have materialized, while others have not and have been supplanted by newer approaches. Current applications of measuring PVF have included: differentiating constrictive pericarditis from restriction, estimation of left ventricular (LV) filling pressures, evaluation of LV diastolic dysfunction and left atrial (LA) function, and grading the severity of mitral regurgitation (MR). However, there have been a number of controversies raised in the use of PVF profiles. Using transthoracic echocardiography, there may be technical issues in measuring the atrial reversal flow velocity. The use of PVF in the evaluation of the severity of MR is not always specific and can be affected by atrial fibrillation (AF) and elevated mean LA pressure. Mitral valvuloplasty and radiofrequency ablation for AF, which are the newer applications of PVF in monitoring invasive procedures, are mentioned. This article reviews the important clinical role of Doppler evaluation of PVF, discusses its limitations and pitfalls, and highlights its newer applications.

Catheter Ablation↗

PubMed2003

Comparison of left ventricular diastolic function in obstructive hypertrophic cardiomyopathy in patients undergoing percutaneous septal alcohol ablation versus surgical myotomy/myectomy.

Both percutaneous transcoronary alcohol septal reduction (ASR) and surgical myectomy are effective treatments to relieve left ventricular (LV) outflow tract obstruction in obstructive hypertrophic cardiomyopathy (HC). LV diastolic function was assessed by echocardiography in 57 patients with obstructive HC at baseline and 5 +/- 4 months after ASR (n = 37) or surgical myectomy (n = 20). LV outflow tract pressure gradient decreased from 65 +/- 40 to 23 +/- 21 mm Hg (p <0.01) after treatment. The ratio of the early-to-late peak diastolic LV inflow velocities, and the ratio of the early peak diastolic LV inflow velocity to the lateral mitral annulus early diastolic velocity determined by tissue Doppler imaging significantly decreased after the procedures (1.6 +/- 1.7 vs 1.0 +/- 0.7 and 15 +/- 8 vs 11 +/- 5, respectively), whereas LV inflow propagation velocity significantly increased (60 +/- 24 vs 71 +/- 36 cm/s). Left atrial size decreased from 29 +/- 7 to 25 +/- 6 cm(2) (p <0.05). Patients had a significant improvement in New York Heart Association functional class and in exercise performance. When comparing ASR with myectomy, no difference was found in the degree of change in any parameter of diastolic function. Thus, diastolic function indexes obtained by echocardiography changed after septal reduction interventions in patients with obstructive HC; this change was similar to that after surgical myectomy and ASR.

Adolescent↗

PubMed2003

Geometric differences of the mitral apparatus between ischemic and dilated cardiomyopathy with significant mitral regurgitation: real-time three-dimensional echocardiography study.

BACKGROUND: This study was conducted to elucidate the geometric differences of the mitral apparatus in patients with significant mitral regurgitation caused by ischemic cardiomyopathy (ICM-MR) and by idiopathic dilated cardiomyopathy (DCM-MR) by use of real-time 3D echocardiography (RT3DE). METHODS AND RESULTS: Twenty-six patients with ICM-MR caused by posterior infarction, 18 patients with DCM-MR, and 8 control subjects were studied. With the 3D software, commissure-commissure plane and 3 perpendicular anteroposterior (AP) planes were generated for imaging the medial, central, and lateral sides of the mitral valve (MV) during mid systole. In 3 AP planes, the angles between the annular plane and each leaflet (anterior, Aalpha; posterior, Palpha) were measured. In ICM-MR, Aalpha measured in the medial and central planes was significantly larger than that in the lateral plane (39+/-5 degrees, 34+/-6 degrees, and 27+/-5 degrees, respectively; P<0.01), whereas Palpha showed no significant difference in any of the 3 AP planes (61+/-7 degrees, 57+/-7 degrees, and 56+/-7 degrees, P>0.05). In DCM-MR, both Aalpha (38+/-8 degrees, 37+/-9 degrees, and 36+/-7 degrees, P>0.05) and Palpha (59+/-6 degrees, 58+/-5 degrees, and 57+/-6 degrees, P>0.05) revealed no significant differences in the 3 planes. CONCLUSIONS: The pattern of MV deformation from the medial to the lateral side was asymmetrical in ICM-MR, whereas it was symmetrical in DCM-MR. RT3DE is a helpful tool for differentiating the geometry of the mitral apparatus between these 2 different types of functional mitral regurgitation.

Cardiomyopathies↗

PubMed2003

Myeloperoxidase and plasminogen activator inhibitor 1 play a central role in ventricular remodeling after myocardial infarction.

Left ventricular (LV) remodeling after myocardial infarction (MI) results in LV dilation, a major cause of congestive heart failure and sudden cardiac death. Ischemic injury and the ensuing inflammatory response participate in LV remodeling, leading to myocardial rupture and LV dilation. Myeloperoxidase (MPO), which accumulates in the infarct zone, is released from neutrophils and monocytes leading to the formation of reactive chlorinating species capable of oxidizing proteins and altering biological function. We studied acute myocardial infarction (AMI) in a chronic coronary artery ligation model in MPO null mice (MPO(-/-)). MPO(-/-) demonstrated decreased leukocyte infiltration, significant reduction in LV dilation, and marked preservation of LV function. The mechanism appears to be due to decreased oxidative inactivation of plasminogen activator inhibitor 1 (PAI-1) in the MPO(-/-), leading to decreased tissue plasmin activity. MPO and PAI-1 are shown to have a critical role in the LV response immediately after MI, as demonstrated by markedly delayed myocardial rupture in the MPO(-/-) and accelerated rupture in the PAI-1(-/-). These data offer a mechanistic link between inflammation and LV remodeling by demonstrating a heretofore unrecognized role for MPO and PAI-1 in orchestrating the myocardial response to AMI.

Animals↗

PubMed2003

Blockade of the platelet P2Y12 receptor by AR-C69931MX sustains coronary artery recanalization and improves the myocardial tissue perfusion in a canine thrombosis model.

OBJECTIVE: Reperfusion therapy for myocardial infarction is limited by a significant reocclusion rate and less optimal myocardial tissue perfusion due to excessive platelet accumulation and recruitment at the sites of vascular injury. We assessed the influence of a selective P2Y(12)-receptor antagonist (AR-C69931MX), in conjunction with thrombolytic therapy, on the prevention of platelet aggregation and thrombus formation. METHODS AND RESULTS: A canine coronary electrolytic injury thrombosis model was used. Tissue-type plasminogen activator (t-PA; 1 mg/kg in phase I, 0.5 mg/kg in phase II in the AR-C69931MX group, and 1 mg/kg in the placebo group in phase I and II) was administered 30 minutes after thrombus formation; either saline or AR-C69931MX (4 micro g x kg(-1) x min(-1)) was given to all animals intravenously 10 minutes before t-PA administration for a total of 2 hours. All animals received heparin (80 U/kg) as an intravenous bolus followed by a continuous infusion of 17 U x kg(-1) x h(-1). Myocardial tissue perfusion was evaluated by use of the colored microsphere technique and real-time myocardial contrast echocardiography. The incidences of reocclusion and cyclic flow variation were significantly decreased in the AR-C69931MX group (P<0.05). Myocardial tissue flow with AR-C69931MX treatment improved significantly at 20 and 120 minutes after reflow, whereas tissue flow with placebo remained at a level similar to that during occlusion (P<0.05). CONCLUSIONS: The adjunctive administration of AR-C69931MX blocked ADP-mediated platelet aggregation and recruitment and prevented platelet-mediated thrombosis, resulting in prolongation of reperfusion time and a decrease in reocclusion and cyclic flow variations. Importantly, myocardial tissue perfusion was significantly improved in the P2Y(12) antagonist group.

Adenosine Monophosphate↗

PubMed2003

False-positive exercise echocardiograms: impact of sex and blood pressure response.

BACKGROUND: Factors related to false-positive results of exercise echocardiography (ExE) to diagnose coronary disease have not been extensively studied. In addition, previous studies were performed before routine use of digital and tissue harmonic imaging. We evaluated the clinical and echocardiographic predictors of false-positive results during ExE. METHODS: Four hundred sixty-four patients who had both coronary angiography and ExE were enrolled retrospectively. Significant coronary disease was defined by stenoses > or =50% lumen diameter. RESULTS: Fifty-eight (13%) had false-positive results. Thirty-one (53%) of these patients were women, which was significantly higher than the percentage of women (25%) in the true-positive group (P <.001). Average peak systolic blood pressure (BP) in the false-positive group was significantly higher than in the true-positive group. Test specificity was decreased at higher levels of BP without change of sensitivity. Men demonstrated a decrease in specificity at peak systolic BP > or =200 mm Hg, whereas women showed a sharp decrease in specificity at BP > or =180 mm Hg. Wall motion score index (WMSI) after peak exercise and the proportion of high- and intermediate-risk patients according to Duke score were significantly lower in the false-positive than in the true-positive group. CONCLUSIONS: The factors predictive of false-positive results during ExE to diagnose coronary disease were female sex, higher BP at peak exercise, lower risk by Duke score and lower number of abnormal segments and wall motion score index after peak exercise. Women appear to be susceptible to wall motion abnormalities caused by elevated exercise BP. These variables should be considered in the interpretation of ExE.

Adult↗

PubMed2003

Prediction of mortality in patients without angina: use of an exercise score and exercise echocardiography.

BACKGROUND: Exercise testing has limited efficacy for identifying coronary artery disease (CAD) in the absence of anginal symptoms. Exercise echocardiography is more accurate than standard exercise testing, but its efficacy in this situation has not been defined. We sought to identify whether the Duke treadmill score or exercise echocardiography (ExE) could be used to identify risk in patients without anginal symptoms. METHODS: We studied 1859 patients without typical or atypical angina, heart failure, or a history or ECG evidence of infarction or CAD, who were referred for ExE, of whom 1832 (age 51+/-15 years, 944 men) were followed for up to 10 years. The presence and extent of ischaemia and scar were interpreted by expert reviewers at the time of the original study. RESULTS: Exercise provoked significant (>0.1mV) ST segment depression in 215 patients (12%), and wall motion abnormalities in 137 (8%). Seventy-eight patients (4%) died before revascularization, only 17 from known cardiac causes. The independent predictors of death were age (RR 1.1, p<0.0001), smoking, Duke treadmill score (RR 0.9, p<0.0001) and resting LV dysfunction (RR 1.9, p<0.04), but did not include ischaemia at ExE. Echocardiography was not predictive of outcome in subgroups with an intermediate or high risk Duke score, nor in patients with two or more risk factors. CONCLUSIONS: Patients without anginal symptoms have a low mortality, especially from cardiac causes. If such individuals undergo exercise testing and a resting echocardiogram, exercise echocardiography does not offer additional prognostic information.

Aged↗

PubMed2003

An evaluation of the use of new Doppler methods for detecting longitudinal function abnormalities in a pacing-induced heart failure model.

BACKGROUND: Doppler tissue echocardiography and color M-mode Doppler flow propagation velocity have proven useful in evaluating cross-sections of patients with left ventricular (LV) dysfunction, but experience with serial changes is limited. PURPOSE AND METHODS: We tested their use by evaluating the temporal changes of LV function in a pacing-induced congestive heart failure model. Rapid ventricular pacing was initiated and maintained in 20 dogs for 4 weeks. Echocardiography was performed at baseline and weekly during brief pacing cessation. RESULTS: With rapid pacing, LV volume significantly increased and ejection fraction (57%-28%), stroke volume (37-18 mL), and mitral annulus systolic velocity (16.1-6.6 cm/s) by Doppler tissue echocardiography significantly decreased, with ejection fraction and mitral annulus systolic velocity closely correlated (r = 0.706, P <.0001). In contrast to the mitral inflow velocities, mitral annulus early diastolic velocity decreased steadily (12.3-7.3 cm/s) resulting in a dramatic decrease in mitral annulus early/late (1.22-0.57) diastolic velocity with no tendency toward pseudonormalization. The color M-mode Doppler flow propagation velocity also showed significant steady decrease (57-24 cm/s) throughout the pacing period. Multiple regression analysis chose mitral annulus systolic velocity (r = 0.895, P <.0001) and propagation velocity (r = 0.782, P <.0001) for the most important factor predicting LV systolic and diastolic function, respectively. CONCLUSIONS: Doppler tissue echocardiography and color M-mode Doppler flow could evaluate the serial deterioration in LV dysfunction throughout the pacing period. These were more useful in quantifying progressive LV dysfunction than conventional ehocardiographic techniques, and were probably relatively independent of preload. These techniques could be suitable for longitudinal evaluation in addition to the cross-sectional study.

Animals↗

PubMed2003

Comparative value of single-beat load-independent contractility indices in dilated cardiomyopathy and mitral regurgitation.

OBJECTIVE: We sought to compare single-beat estimates of contractility indices. METHODS: Echocardiography was performed for 6 control patients, 8 patients with dilated cardiomyopathy, and 9 patients with mitral regurgitation (MR). Left ventricular volume waveform, outflow tract velocities, and mitral annulus velocities were recorded with carotid tonometry. Numeric simulations were used to generate the same data while varying contractility, compliance, and MR. Estimates of elastance (normalized systolic and bilinearly approximated), preload-recruitable stroke work, and preload-adjusted maximal power were calculated. RESULTS: Normalized systolic and bilinearly approximated elastance were decreased in patients with dilated cardiomyopathy (P <.005 for both) and MR (P =.0002 and.02, respectively). Preload-recruitable stroke work and preload-adjusted maximal power were decreased in patients with dilated cardiomyopathy only (P <.005 for both). Simulations confirmed that these differences are a result of dissimilar behavior of estimates if MR or compliance change. CONCLUSIONS: Single-beat indices are decreased in dilated cardiomyopathy, but in MR show dissimilar behavior.

Adult↗

PubMed2003

Mutual information-based multimodality registration of cardiac ultrasound and SPECT images: a preliminary investigation.

BACKGROUND: Ultrasound (US) and single photon emission computed tomography (SPECT) are the two most commonly prescribed procedures for diagnosing coronary artery disease (CAD). We have demonstrated the feasibility of multimodality registration of two-dimensional (2D) and three-dimensional (3D) cardiac US images with cardiac SPECT images with an aim to simultaneously present the complementary anatomical and perfusion information from the two modalities. We have also tested the clinicians' assessment of the clinical adequacy of the registered images. METHODS AND RESULTS: We have demonstrated temporal and spatial registration for nine sets of cardiac US and SPECT cine loops covering the entire cardiac cycle. Temporal alignment was performed by interpolation of existing SPECT images at cardiac phases corresponding to available US images. Spatial registration was performed in 3D image space using a mutual information-based approach. Experts from echocardiography and nuclear medicine determined the clinical utility of the registration by rating each registration on a scale of 1 to 5, a rating of 3 or above indicating clinical utility. 2DUS-SPECT registration (five cases) received an average rating of 4.2, whereas 3DUS-SPECT registration (four cases) received an average rating of 2.85. By one-sample t test, the overall evaluations (mean 3.58) were greater than the pre-specified clinical cut-off of 3 with p < 0.05, indicating likelihood of clinical utility. CONCLUSION: Our method demonstrates the feasibility of registering cardiac US and SPECT images in their present as well as possible future forms. Such registration has the potential to provide a more accurate and powerful tool for diagnosing CAD.

Clinical Protocols↗

PubMed2003

Real-time three-dimensional color doppler evaluation of the flow convergence zone for quantification of mitral regurgitation: Validation experimental animal study and initial clinical experience.

BACKGROUND: Pitfalls of the flow convergence (FC) method, including 2-dimensional imaging of the 3-dimensional (3D) geometry of the FC surface, can lead to erroneous quantification of mitral regurgitation (MR). This limitation may be mitigated by the use of real-time 3D color Doppler echocardiography (CE). Our objective was to validate a real-time 3D navigation method for MR quantification. METHODS: In 12 sheep with surgically induced chronic MR, 37 different hemodynamic conditions were studied with real-time 3DCE. Using real-time 3D navigation, the radius of the largest hemispherical FC zone was located and measured. MR volume was quantified according to the FC method after observing the shape of FC in 3D space. Aortic and mitral electromagnetic flow probes and meters were balanced against each other to determine reference MR volume. As an initial clinical application study, 22 patients with chronic MR were also studied with this real-time 3DCE-FC method. Left ventricular (LV) outflow tract automated cardiac flow measurement (Toshiba Corp, Tokyo, Japan) and real-time 3D LV stroke volume were used to quantify the reference MR volume (MR volume = 3DLV stroke volume - automated cardiac flow measurement). RESULTS: In the sheep model, a good correlation and agreement was seen between MR volume by real-time 3DCE and electromagnetic (y = 0.77x + 1.48, r = 0.87, P <.001, delta = -0.91 +/- 2.65 mL). In patients, real-time 3DCE-derived MR volume also showed a good correlation and agreement with the reference method (y = 0.89x - 0.38, r = 0.93, P <.001, delta = -4.8 +/- 7.6 mL). CONCLUSIONS: real-time 3DCE can capture the entire FC image, permitting geometrical recognition of the FC zone geometry and reliable MR quantification.

Adult↗

PubMed2003

Use of strain imaging in detecting segmental dysfunction in patients with hypertrophic cardiomyopathy.

BACKGROUND: The distribution and magnitude of left ventricular hypertrophy are not uniform in patients with hypertrophic cardiomyopathy (HCM). Previous echocardiographic studies have focused on global left ventricular function. Recently, myocardial Doppler strain (epsilon) imaging, a newly developed technique, has allowed the quantification of regional myocardial motion. The aim of this study was to characterize regional left ventricular systolic function by myocardial Doppler epsilon imaging in patients with HCM. METHODS: Included in this study were 31 patients with asymmetric septal hypertrophy and HCM, and 41 age-matched healthy patients. Regional longitudinal axial systolic epsilon was assessed at the basal, mid, and apical segments of the septal and lateral walls and compared between both groups. RESULTS: Patients with HCM had reduced epsilon at the ventricular septum (-10.3 +/- 5.7%) compared with control patients (-19.4 +/- 3.3%, P <.001). In the HCM group, epsilon in the midseptum (-1.3 +/- 8.2%) was significantly less than at the basal (-12.2 +/- 8.7%, P <.01) and apical septum (-17.3 +/- 10.4%, P <.01), and was also less than at the midlateral wall (-9.4 +/- 5.3%, P <.05). There was a significant correlation between midseptal epsilon and intraventricular septum to posterior wall thickness ratio (r = 0.81, P <.001). CONCLUSION: Midseptal longitudinal epsilon was markedly decreased, even reversed in patients with HCM (paradoxic longitudinal systolic expansion), which was directly related to the degree of septal hypertrophy. Myocardial Doppler epsilon imaging could offer a unique approach to quantify regional systolic dysfunction in these patients.

Adult↗

PubMed2003

A new automated method for the quantification of mitral regurgitant volume and dynamic regurgitant orifice area based on a normalized centerline velocity distribution using color M-mode and continuous wave Doppler imaging.

Previous echocardiographic techniques for quantifying valvular regurgitation (PISA) are limited by factors including uncertainties in orifice location and hemispheric convergence assumption. Using computational fluid dynamics simulations, we developed a new model for the estimation of orifice diameter and regurgitant volume without the aforementioned assumptions of the PISA technique. Using experimental data obtained from the in vitro flow model we successfully validated our new model. The model output (y) and reference (x) values were in close agreement (y = 0.95x + 0.38, r = 0.96, error = 1.68 +/- 7.54% for the orifice diameter and y = 1.18x - 4.72, r = 0.93, error = 6.48 +/- 16.81% for the regurgitant volume).

Aortic Valve Insufficiency↗

PubMed2003

Determinants of the development of mitral regurgitation in pacing-induced heart failure.

The pacing-induced heart failure model provides an opportunity to assess the structural and functional determinants of mitral regurgitation (MR) in dilated cardiomyopathy. This study aimed to evaluate MR to better understand the multitude of factors contributing to its development. Heart failure was induced by rapid ventricular pacing (230 beats/min) in 40 mongrel dogs. Left ventricular (LV) size and MR were evaluated echocardiographically. LV contractility was analyzed using a conductance catheter. MR increased to mild in 12 animals (regurgitant orifice area, 0.06+/-0.05 cm(2)), moderate in 15 (0.14+/-0.07 cm(2)), and severe in 13 (0.34+/-0.16 cm(2)). The grade of MR had an inverse relationships with E(max) (the slope of the end-systolic pressure-volume relationship, p<0.01) and dE/dt (the slope of the maximum rate of change of pressure-end-diastolic volume [V(ED)] relationship, p<0.01) and positive relationships with V(ED) and end-diastolic cross-sectional areas and lengths (p<0.05) by univariate analysis. The dE/dt had an independently significant (p<0.01) relationship by multivariable logistic regression. Many factors influence the development of MR and because of its similarity to the clinical situation, this model can be used to investigate MR and heart failure, as well as new surgical therapies.

Animals↗

PubMed2003

Echocardiographic and hemodynamic evaluation of cardiovascular performance during laparoscopy of morbidly obese patients.

BACKGROUND: The effects of morbid obesity, pneumoperitoneum (PP) and body position on cardiac function during laparoscopy were studied. METHODS: Transesophageal echocardiography (TEE) was performed on 10 obese patients (body mass index, BMI, 48.1+/-1.8 kg/m2) and 10 normal weight patients (BMI = 22.6+/-0.8 kg/m2) in supine, Trendelenburg and reverse Trendelenburg positions before and after PP. Left ventricular end-systolic wall stress (LVESWS) was calculated from invasive blood pressure (BP) values and LV dimensions obtained by TEE. Diastolic filling was assessed by mitral valve and pulmonary vein flow velocities. RESULTS: LVESWS was higher in obese patients both at baseline (46.0+/-4.0 x 10(3) dyn/cm2) and with PP (69.3+/-8.2 x 10(3) dyn/cm2), than normal weight subjects (31.9+/-3.7 x 10(3) dyn/cm2 and 45.7+/-5.9 x 10(3) dyn/cm2; P <0.05 obese vs normal weight patients at baseline). Systolic BP was not different between groups at baseline (normal weight 111+/-4 mmHg, obese 119+/-3 mmHg), but increased significantly with PP only in obese patients (normal weight 129+/-6 mmHg, obese 157+/-8 mmHg; P <0.05). Postural changes during PP had no impact on cardiac function in either obese or normal weight subjects. CONCLUSIONS: Anesthetized obese patients undergoing laparoscopy have higher LVESWS before pneumoperitoneum (due to increased end-systolic left ventricular dimensions) and during pneumoperitoneum (due to more pronounced increases in blood pressure). Since LVESWS is a determinant of myocardial oxygen demand, more aggressive control of blood pressure (ventricular afterload) in MO patients may be warranted to optimize the myocardial oxygen requirements.

Adult↗

PubMed2002

Left ventricular outflow tract mean systolic acceleration as a surrogate for the slope of the left ventricular end-systolic pressure-volume relationship.

OBJECTIVE: The goal of this study was to analyze left ventricular outflow tract systolic acceleration (LVOT(Acc)) during alterations in left ventricular (LV) contractility and LV filling. BACKGROUND: Most indexes described to quantify LV systolic function, such as LV ejection fraction and cardiac output, are dependent on loading conditions. METHODS: In 18 sheep (4 normal, 6 with aortic regurgitation, and 8 with old myocardial infarction), blood flow velocities through the LVOT were recorded using conventional pulsed Doppler. The LVOT(Acc) was calculated as the aortic peak velocity divided by the time to peak flow; LVOT(Acc) was compared with LV maximal elastance (E(m)) acquired by conductance catheter under different loading conditions, including volume and pressure overload during an acute coronary occlusion (n = 10). In addition, a clinically validated lumped-parameter numerical model of the cardiovascular system was used to support our findings. RESULTS: Left ventricular E(m) and LVOT(Acc) decreased during ischemia (1.67 +/- 0.67 mm Hg.ml(-1) before vs. 0.93 +/- 0.41 mm Hg.ml(-1) during acute coronary occlusion [p < 0.05] and 7.9 +/- 3.1 m.s(-2) before vs. 4.4 +/- 1.0 m.s(-2) during coronary occlusion [p < 0.05], respectively). Left ventricular outflow tract systolic acceleration showed a strong linear correlation with LV E(m) (y = 3.84x + 1.87, r = 0.85, p < 0.001). Similar findings were obtained with the numerical modeling, which demonstrated a strong correlation between predicted and actual LV E(m) (predicted = 0.98 [actual] -0.01, r = 0.86). By analysis of variance, there was no statistically significant difference in LVOT(Acc) under different loading conditions. CONCLUSIONS: For a variety of hemodynamic conditions, LVOT(Acc) was linearly related to the LV contractility index LV E(m) and was independent of loading conditions. These findings were consistent with numerical modeling. Thus, this Doppler index may serve as a good noninvasive index of LV contractility.

Acceleration↗

PubMed2002

Slow rate during AF improves ventricular performance by reducing sensitivity to cycle length irregularity.

Atrial fibrillation (AF) is characterized by short and irregular ventricular cycle lengths (VCL). While the beneficial effects of heart rate slowing (i.e., the prolongation of VCL) in AF are well recognized, little is known about the impact of irregularity. In 10 anesthetized dogs, R-R intervals, left ventricular (LV) pressure, and aortic flow were collected for >500 beats during fast AF and when the average VCL was prolonged to 75%, 100%, and 125% of the intrinsic sinus cycle length by selective atrioventricular (AV) nodal vagal stimulation. We used the ratio of the preceding and prepreceding R-R intervals (RR(p)/RR(pp)) as an index of cycle length irregularity and assessed its effects on the maximum LV power, the minimum of the first derivative of LV pressure, and the time constant of relaxation by using nonlinear fitting with monoexponential functions. During prolongation of VCL, there was a pronounced decrease in curvature with the formation of a plateau, indicating a lesser dependence on RR(p)/RR(pp). We conclude that prolongation of the VCL during AF reduces the sensitivity of the LV performance parameters to irregularity.

Animals↗

PubMed2002

Survival after aortic valve replacement for severe aortic stenosis with low transvalvular gradients and severe left ventricular dysfunction.

OBJECTIVE: We sought to assess whether aortic valve replacement (AVR) among patients with severe aortic stenosis (AS), severe left ventricular (LV) dysfunction and a low transvalvular gradient (TVG) is associated with improved survival. BACKGROUND: The optimal management of patients with severe AS with severe LV dysfunction and a low TVG remains controversial. METHODS: Between 1990 and 1998, we evaluated 68 patients who underwent AVR at our institution (AVR group) and 89 patients who did not undergo AVR (control group), with an aortic valve area < or = 0.75 cm(2), LV ejection fraction < or = 35% and mean gradient < or = 30 mm Hg. Using propensity analysis, survival was compared between a cohort of 39 patients in the AVR group and 56 patients in the control group. RESULTS: Despite well-matched baseline characteristics among propensity-matched patients, the one- and four-year survival rates were markedly improved in patients in the AVR group (82% and 78%), as compared with patients in the control group (41% and 15%; p < 0.0001). By multivariable analysis, the main predictor of improved survival was AVR (adjusted risk ratio 0.19, 95% confidence interval 0.09 to 0.39; p < 0.0001). The only other predictors of mortality were age and the serum creatinine level. CONCLUSIONS: Among select patients with severe AS, severe LV dysfunction and a low TVG, AVR was associated with significantly improved survival.

Adult↗