PubMed Health⌕ Search

Biomedical subjects

Alan D Waggoner

Publications and source records attributed to Alan D Waggoner.

At least 19 recordsLinked to original sources
PubMed2007

Cardiac resynchronization therapy and the emerging role of echocardiography (part 1): indications and results from current studies.

Cardiac resynchronization therapy (CRT) has been established as an adjunctive treatment for patients with left ventricular systolic dysfunction and medically refractory heart failure with a wide QRS interval. Echocardiography can be used to determine the response in left ventricular structure and function after device implantation and emerging evidence as a method for selection of patients who may derive clinical benefit from CRT. This review discusses the applications of CRT, including results of clinical trials and the current experience using echocardiography. Part 2 will address the practical aspects of obtaining echocardiographic data in patients who are potential candidates for CRT and optimization of pacemaker settings after device implantation.

Cardiac Pacing, Artificial↗
PubMed2007

Cardiac resynchronization therapy and the emerging role of echocardiography (part 2): the comprehensive examination.

Cardiac resynchronization therapy has been established as an adjunctive treatment for patients with severe left ventricular systolic dysfunction and medically refractory heart failure symptoms with a prolonged electrocardiographic QRS interval. Echocardiography has emerged as a useful method to evaluate patients who are considered for cardiac resynchronization therapy. This review outlines measurements of ventricular performance to be used in this patient population including echocardiographic optimization of cardiac resynchronization therapy device settings.

Cardiac Pacing, Artificial↗
PubMed2006

Relation of left ventricular lead placement in cardiac resynchronization therapy to left ventricular reverse remodeling and to diastolic dyssynchrony.

The effects of left ventricular (LV) lead placement for cardiac resynchronization therapy (CRT) on LV remodeling and dyssynchrony are not well defined. Sixty-one patients (age 60 +/- 11 years, 76% men) were evaluated by echocardiography before and 4 +/- 2 months after CRT and grouped by the LV lead placement (lateral, posterolateral, or anterolateral). Echocardiographic measurements included LV volumes and LV ejection fraction. Tissue Doppler imaging was used to assess for inter- and intraventricular systolic and diastolic dyssynchrony. Analysis of variance was used to determine the effect of the LV lead placement on echocardiographic variables after CRT. The LV lead was placed in a lateral cardiac vein in 33 patients (54%), posterolateral in 15 (25%), and anterior in 13 (21%). Lateral LV lead placement was associated with significantly smaller LV volumes compared with the posterolateral lead placement (p <0.01). Diastolic dyssynchrony improved significantly with lateral lead placement compared with the anterior lead location (p <0.05). Improvement in LV ejection fraction and inter- and intraventricular systolic dyssynchrony was similar among the 3 groups. In conclusion, in patients undergoing CRT, a lateral lead location resulted in greater reverse LV remodeling and improved diastolic dyssynchrony compared with other lead placement locations.

Diastole↗
PubMed2006

Clinical outcomes after cardiac resynchronization therapy: importance of left ventricular diastolic function and origin of heart failure.

BACKGROUND: Cardiac resynchronization therapy (CRT) improves functional outcomes in patients with severe systolic heart failure. Whether the effects of CRT on left ventricular (LV) diastolic function and clinical outcomes are influenced by the cause as either ischemic or nonischemic cardiomyopathy (CM) has not been well established. METHODS: A total of 57 patients (age 60 +/- 11 years; 25% women; LV ejection fraction 25 +/- 5%) were studied before and 4 +/- 2 months after CRT by echocardiography. Heart failure cause was ischemic CM in 19 and nonischemic CM in 38. Measurements of LV systolic and diastolic function were determined by 2-dimensional and Doppler echocardiography with Doppler tissue imaging of regional myocardial velocities. Clinical outcome events were assessed at long-term follow-up and included hospitalization for heart failure exacerbation, heart transplantation, or cardiac-related death. RESULTS: There were significant increases in LV ejection fraction, reductions in end-systolic volumes, and improved LV systolic dyssynchrony in both groups. However, significant improvements in LV diastolic function were observed only in the patients with nonischemic CM. Clinical events occurred in 53% of the ischemic group versus 26% of the nonischemic group (P < .05) after 20 +/- 11 months of CRT. Univariate and multivariate analysis revealed that Doppler-estimated LV filling pressures were predictors of clinical outcome events. CONCLUSIONS: After CRT patients with ischemic CM exhibit lack of improvement in LV diastolic function despite favorable effects on LV systolic performance. The Doppler-derived LV filling indices may be an important predictor of long-term clinical outcomes after CRT.

Cardiac Pacing, Artificial↗
PubMed2006

Alterations in left ventricular structure and function in type-1 diabetics: a focus on left atrial contribution to function.

This study was designed to determine the effects of type 1 diabetes mellitus (T1DM) on left ventricular (LV) and particularly left atrial (LA) structure and function. We evaluated 88 non-obese subjects: 44 with T1DM, 44 age- and gender-matched normal controls (age 39 +/- 11 years). LV and LA structure and function were quantified using two-dimensional echocardiography, pulse-wave Doppler, and tissue Doppler imaging, including early and late diastolic myocardial velocities (Em global and Am global, respectively). The T1DM subjects averaged higher heart rate, relative wall thickness, and ejection fraction, and lower indexed end-systolic volume than normal controls (P < .001, P < .05, P = .01, and P < .05, respectively). T1DM was related to A wave velocity, Am global, A wave integral, LA ejection fraction, and LA systolic ejection fraction (P < .01, P < .05, P < .0005, P < .001, and P < .0005, respectively). In multivariate analyses, T1DM was an independent predictor of the A wave integral, LA ejection fraction, and LA systolic ejection fraction (P < .01, P < .01, and P < .005, respectively). Thus, despite increased relative wall thickness, LV systolic function is increased and early diastolic filling is normal in T1DM subjects; however, they possess changes in LA transport function suggesting increased reliance on LA contribution to LV filling.

Adolescent↗
PubMed2006

Characterization of left ventricular diastolic function in hypertension by use of Doppler tissue imaging and color M-mode techniques.

BACKGROUND: Abnormalities in left ventricular (LV) relaxation and/or increased filling pressures are indicators of LV diastolic dysfunction in patients with hypertension (HTN). The purpose of this study was to assess clinical use of pulsed wave Doppler, Doppler tissue imaging (DTI), and color M-mode (CMM) indices for determination of diastolic function in patients with HTN. METHODS: In all, 278 ambulatory patients with normal LV systolic function were grouped according to the presence of HTN with and without LV hypertrophy (LVH) (determined by the 2-dimensional area-length method) as follows: healthy control subjects (NC, n = 122), HTN without LVH (HTN, n = 70), and HTN with LVH (HTN+LVH, n = 86). Pulsed wave Doppler-derived measurements included transmitral E- and A-wave velocities, E/A ratio, and deceleration and isovolumic relaxation time intervals; DTI-derived early diastolic (Em) velocities were obtained at 4 LV annular sites. CMM-derived flow propagation velocity and the intraventricular pressure gradient were also calculated. Analysis of covariance adjusted for age and sex of diastolic indices was performed to compare the differences among groups. RESULTS: Only DTI-derived filling pressures demonstrated progressive statistically significant differences among all 3 groups (ie, HTN vs NC, HTN+LVH vs NC, and HTN vs HTN+LVH). However, CMM-derived flow propagation velocity and intraventricular pressure gradient indices were similar among the groups. CONCLUSION: DTI is a robust method compared with pulsed wave Doppler- and CMM-derived indices for the quantitative assessment of LV relaxation and filling pressures in patients with HTN.

Echocardiography, Doppler, Color↗
PubMed2006

N-terminal pro B-type natriuretic peptide levels: correlation with echocardiographically determined left ventricular diastolic function in an ambulatory cohort.

OBJECTIVES: To investigate the correlations of plasma N-terminal pro B-type natriuretic peptide (NT-proBNP) levels with echocardiographic measurements of left ventricular (LV) systolic and/or diastolic function. BACKGROUND: Plasma levels of NT-proBNP are increased in heart failure. The extent to which NT-proBNP levels increase in LV diastolic dysfunction has not been well characterized. METHODS: Plasma NT-proBNP levels were measured in 191 consecutive, clinically stable, ambulatory patients. Echocardiography was used to determine LV systolic (LV ejection fraction [LVEF]) and diastolic function by mitral E wave to Doppler tissue early diastolic lateral annulus velocity ratio (E/Em). Patients with a history, physical findings, and/or echocardiographic evidence of cardiovascular disease (n = 148) were grouped as: (1) normal LV systolic function (LVEF > or = 55%, n = 81); and (2) LV systolic dysfunction (LVEF < 55%, n = 67). They were compared to a group of healthy control subjects (n = 43). Multivariate regression analyses were used to determine significant correlations with plasma NT-proBNP levels. RESULTS: NT-proBNP levels correlated negatively with LVEF (P < .001) and positively with E/Em (P = .001). Multivariate regression analysis demonstrated a significant correlation of NT-proBNP levels with LVEF (P < .001) and E/Em (P = .03). CONCLUSIONS: In this clinically stable, ambulatory cohort of patients with cardiovascular disease and healthy control subjects, plasma NT-proBNP levels were significantly higher in those with LV systolic dysfunction and/or elevated filling pressures, independent of the effects of LV mass, renal function, and age. These results suggest that NT-proBNP levels may be a useful adjunct in the characterization of patients presenting with history and/or symptoms compatible with LV systolic and/or diastolic dysfunction.

Ambulatory Care↗
PubMed2006

Prospective comparison of echocardiographic atrioventricular delay optimization methods for cardiac resynchronization therapy.

BACKGROUND: Atrioventricular (AV) delay optimization can be an important determinant of the response to cardiac resynchronization therapy (CRT) in patients with medically refractory heart failure and a ventricular conduction delay. OBJECTIVES: The purpose of this study was to compare two Doppler echocardiographic methods of AV delay optimization after CRT. METHODS: Forty consecutive patients (age 59 +/- 12 years) with severe heart failure, New York Heart Association class 3.1 +/- 0.4, QRS duration 177 +/- 23 ms, and left ventricular ejection fraction 26% +/- 6% referred for CRT were studied using two-dimensional Doppler echocardiography. In each patient, the acute improvement in stroke volume with CRT in response to two methods of AV delay optimization was compared. In the first method, the AV delay that produced the largest increase in the aortic velocity time integral (VTI) derived from continuous-wave Doppler (aortic VTI method) was measured. In the second method, the AV delay that optimized the timing of mitral valve closure to occur simultaneously with the onset of left ventricular systole was calculated from pulsed Doppler mitral waveforms at a short and long AV delay interval (mitral inflow method). RESULTS: The optimized AV delay determined by the aortic VTI method resulted in an increase in aortic VTI of 19% +/- 13% compared with an increase of 12% +/- 12% by the mitral inflow method (P <.001). The optimized AV delay by the aortic VTI method was significantly longer than the optimized AV delay calculated from the mitral inflow method (119 +/- 34 ms vs 95 +/- 24 ms, P <.001). There was no correlation in the AV delay determined by the two methods (r = 0.03). CONCLUSION: AV delay optimization by Doppler echocardiography for patients with severe heart failure treated with a CRT device yields a greater systolic improvement when guided by the aortic VTI method compared with the mitral inflow method.

Atrioventricular Node↗
PubMed2005

Improvements in left ventricular diastolic function after cardiac resynchronization therapy are coupled to response in systolic performance.

OBJECTIVES: To determine the short-term effects of cardiac resynchronization therapy (CRT) on measurements of left ventricular (LV) diastolic function in patients with severe heart failure. BACKGROUND: Cardiac resynchronization therapy improves systolic performance; however, the effects on diastolic function by load-dependent pulsed-wave Doppler transmitral indices has been variable. METHODS: Fifty patients with severe heart failure were evaluated by two-dimensional Doppler echocardiography immediately prior to and 4 +/- 1 month after CRT. Measurements included LV volumes and ejection fraction (EF), pulsed-wave Doppler (PWD)-derived transmitral filling indices (E- and A-wave velocities, E/A ratio, deceleration time [DT], diastolic filling time [DFT], and isovolumic relaxation time). Tissue Doppler imaging was used for measurements of systolic and diastolic (Em) velocities at four mitral annular sites; mitral E-wave/Em ratio was calculated to estimate LV filling pressure. Color M-mode flow propagation velocities were also obtained. RESULTS: After CRT, LV volumes decreased significantly (p < 0.001) and LVEF increased >5% in 28 of 50 patients (56%) and were accompanied by reduction in PWD mitral E-wave velocity and E/A ratio (both p < 0.01), increased DT and DFT (both p < 0.01), and lower filling pressures (i.e., E-wave/Em septal; p < 0.01). Patients with LVEF response < or =5% after CRT had no significant changes in measurements of diastolic function; LV relaxation (i.e., Em velocities) worsened in this group. CONCLUSIONS: In heart failure patients receiving CRT, improvement in LV diastolic function is coupled to the improvement in LV systolic function.

Aged↗
PubMed2005

The research grant process: a reference guide for cardiovascular sonographers.

Opportunities for sonographer-initiated research have increased during the past decade. Although research has traditionally been viewed as a nonclinical activity, funding is available for clinical problems. This article aims to increase sonographer awareness of this unique opportunity, encourage the submission of grant proposals, and enhance the understanding of the grant writing process. This review discusses the procedures involved in planning a research project while describing the structure of the research grant proposal including specific aims, background, preliminary studies, methods, potential limitations, significance, budget, and references.

Echocardiography↗
PubMed2005

Cardiac resynchronization therapy acutely improves diastolic function.

BACKGROUND: Invasive studies have shown that cardiac resynchronization therapy (CRT) acutely improves left ventricular (LV) systolic performance and lowers filling pressures in a majority of patients with medically-refractory severe heart failure. Measurements included LV volume, ejection fraction, PWD early (E-wave) and atrial (A-wave) velocities, diastolic filling time (DFT), and DTI early diastolic mitral annular velocity (Em) at the lateral and septal annulus; PWD mitral E-wave/Em and E/FP were calculated to estimate LV filling pressures. RESULTS: Immediately after CRT, LV volumes decreased and LVEF increased significantly. PWD mitral E-wave velocity decreased and E-wave duration and DFT increased significantly; mitral E/FP ratio also decreased significantly, consistent with a decrease in LV filling pressure. Patients with a pre-CRT mitral E/A ratio >1 (n = 20), demonstrated improvements in LV diastolic filling and lower filling pressures whereas those with an E/A ratio < or =1 (n = 21) did not show significant changes in diastolic indices. CONCLUSIONS: The acute effects of CRT include echocardiographic evidence of reduced LV volumes and increased LVEF with improved diastolic filling and lower filling pressures; LV relaxation is not significantly altered. The benefits in diastolic function are dependent on the PWD-determined LV filling characteristics prior to CRT.

Cardiac Pacing, Artificial↗
PubMed2005

Plasma triglyceride level is an independent predictor of altered left ventricular relaxation.

BACKGROUND: Diastolic dysfunction, manifested by impaired left ventricular (LV) relaxation, is prevalent among individuals with metabolic disorders. The objective of this study was to evaluate the extent to which plasma triglyceride (TG) levels are related to LV diastolic function. METHODS: A total of 424 subjects (age 49 +/- 12 years) had fasting plasma TG levels measured and underwent echocardiography for assessment of LV structure and function: LV ejection fraction and LV mass indexed to height (LVM/Ht(2.7)); transmitral inflow early diastolic peak velocity (E wave) and late diastolic peak velocity (A wave), and E wave to A wave ratio (E/A); deceleration time; and Doppler tissue imaging early diastolic myocardial velocity (EM), an index of LV relaxation. RESULTS: All subjects had normal LV ejection fraction, 48% had hypertension, 16% had increased LVM/Ht(2.7), 11% had type 2 diabetes mellitus, 37% were obese, and 27% had hypertriglyceridemia (TG > 150 mg/dL). Univariate analysis showed significant relationships between TG level and E/A, deceleration time, and Em (P < or = .001 for all). After adjustment for potential confounders in multivariate models (eg, age, systolic blood pressure, and LVM/Ht(2.7)), TG levels remained predictive of E/A, deceleration time, and Em (P < or = .05, <.001, and < or =.0001, respectively). Stepwise multivariate analysis showed that after age and body mass index, the TG level was the next most predictive variable of Em. CONCLUSIONS: Plasma TG levels show a strong relationship with impaired LV relaxation, an early marker of diastolic dysfunction in human beings. These findings support a hypothesis whereby elevated TG levels favor myocyte intracellular lipid accumulation, possibly leading to lipotoxic diastolic dysfunction.

Female↗
PubMed2004

Prevalence and severity of paravalvular regurgitation in the Artificial Valve Endocarditis Reduction Trial (AVERT) echocardiography study.

OBJECTIVES: The purpose of this study was to determine the prevalence and severity of paravalvular regurgitation (PVR) in the Artificial Valve Endocarditis Reduction Trial (AVERT) cohort. BACKGROUND: The initial AVERT cohort consisted of 807 patients randomized to receive either a Silzone-coated prosthetic valve or a conventional prosthetic valve; early clinical reports showed higher rates of valve explant caused by PVR for Silzone-coated prosthetic valve. METHODS: Of the 678 eligible patients, 575 (85%) underwent postoperative transthoracic echocardiograms. The presence and severity of PVR were identified by color flow Doppler. Reviewers were blinded to the type of prosthetic valve and the demographic and clinical variables. RESULTS: Among those who underwent echocardiography (Silzone-coated prosthetic valve, n = 285 and conventional prosthetic valve, n = 290), 59% had prosthetic aortic valves, 32% prosthetic mitral valves, and 9% had both; demographic and clinical findings (i.e., prosthetic valve endocarditis, thromboembolism, bleeding, and all-cause death) were similar for the two groups. Echocardiographically determined PVR was present in 50 valves: Silzone-coated prosthetic valve, 29 of 285 (10%) and conventional prosthetic valve, 21 of 290 (7%, p = NS); the severity of PVR was similar in both groups. Kaplan-Meier analysis showed no significant differences in PVR at 24 months from valve implantation between the two groups (24-month event-free rate: 93% Silzone-coated prosthetic valve vs. 94% conventional prosthetic valve, p = NS). CONCLUSIONS: Excluding those patients who had initial prosthetic valve explant, the two-year echocardiographic follow-up of the AVERT cohort shows no statistically significant differences in the prevalence or severity of PVR in the Silzone-coated prosthetic valve compared with the conventional prosthetic valve. Further monitoring is warranted to determine whether these clinical outcomes remain similar on long-term follow-up.

Aged↗
PubMed2004

Effect of obesity and insulin resistance on myocardial substrate metabolism and efficiency in young women.

BACKGROUND: Obesity is a risk factor for impaired cardiac performance, particularly in women. Animal studies suggest that alterations in myocardial fatty acid metabolism and efficiency in obesity can cause decreased cardiac performance. In the present study, we tested the hypothesis that myocardial fatty acid metabolism and efficiency are abnormal in obese women. METHODS AND RESULTS: We studied 31 young women (body mass index [BMI] 19 to 52 kg/m2); 19 were obese (BMI >30 kg/m2). Myocardial oxygen consumption (MVO2) and fatty acid uptake (MFAUp), utilization (MFAU), and oxidation (MFAO) were quantified by positron emission tomography. Cardiac work was measured by echocardiography, and efficiency was calculated as work/MVO2. BMI correlated with MVO2 (r=0.58, P=0.0006), MFAUp (r=0.42, P<0.05), and efficiency (r=-0.40, P<0.05). Insulin resistance, quantified by the glucose area under the curve (AUC) during an oral glucose tolerance test, correlated with MFAUp (r=0.55, P<0.005), MFAU (r=0.62, P<0.001), and MFAO (r=0.58, P<0.005). A multivariate, stepwise regression analysis showed that BMI was the only independent predictor of MVO2 and efficiency (P=0.0005 and P<0.05, respectively). Glucose AUC was the only independent predictor of MFAUp, MFAU, and MFAO (P<0.05, <0.005, and <0.005, respectively). CONCLUSIONS: In young women, obesity is a significant predictor of increased MVO2 and decreased efficiency, and insulin resistance is a robust predictor of MFAUp, MFAU, and MFAO. This increase in fatty acid metabolism and decrease in efficiency is concordant with observations made in experimental models of obesity. These metabolic changes may play a role in the pathogenesis of decreased cardiac performance in obese women.

Adult↗
PubMed2004

Alterations in left ventricular structure and function in young healthy obese women: assessment by echocardiography and tissue Doppler imaging.

OBJECTIVES: This study was designed to determine the effects of obesity on left ventricular (LV) structure and function in young obese women. BACKGROUND: Severe prolonged obesity in older adults results in increased plasma volume, eccentric LV hypertrophy, and systolic and diastolic dysfunction. Obese women are at increased risk for the development of heart failure. However, the effects of the obesity on cardiac structure and function in young, otherwise-healthy women are controversial. METHODS: Fifty-one women were evaluated: 20 were obese (body mass index [BMI] > or =30 kg/m(2)) and 31 were non-obese (BMI <30 kg/m(2)). Left ventricular structure and systolic and diastolic function were assessed by two-dimensional echocardiography and tissue Doppler imaging, including the load-independent systolic myocardial velocity (Sm global) and early diastolic myocardial velocity (Em global), respectively. The effects of BMI on LV structure and function were assessed using multivariate regression analyses. RESULTS: Obese women had higher end-diastolic septal and posterior wall thickness, LV mass, and relative wall thickness than non-obese women; BMI values showed significant correlations with these variables (r = 0.58, p < 0.0001; r = 0.50, p < 0.0002; r = 0.52, p < 0.0001, and r = 0.40, p < 0.005, respectively). The Sm global and Em global were lower in obese women, suggesting systolic and diastolic function are decreased; both were negatively correlated with BMI (r = -0.43, p <. 002 and r = -0.61, p < 0.0001, respectively). Multivariate analysis showed BMI was the only independent predictor of relative wall thickness, Sm global, and Em global. CONCLUSIONS: Obesity in young otherwise-healthy women is associated with concentric LV remodeling and decreased systolic and diastolic function. These early abnormalities in LV structure and function may have important implications for explaining the myocardial dysfunction that is associated with increased cardiovascular morbidity and mortality caused by obesity.

Adult↗
PubMed2004

Randomized prospective trial of atrioventricular delay programming for cardiac resynchronization therapy.

OBJECTIVES: The purpose of this study was to determine if AV delay optimization with continuous-wave Doppler aortic velocity-time integral (VTI) is clinically superior to an empiric program in patients treated with cardiac resynchronization therapy (CRT) for severe heart failure. BACKGROUND: The impact of AV delay programming on clinical outcomes associated with CRT is unknown. METHODS: A randomized, prospective, single-blind clinical trial was performed to compare two methods of AV delay programming in 40 patients with severe heart failure referred for CRT. Patients were randomized to either an optimized AV delay determined by Doppler echocardiography (group 1, n = 20) or an empiric AV delay of 120 ms (group 2, n = 20) with both groups programmed in the atriosynchronous biventricular pacing (VDD) mode. Optimal AV delay was defined as the AV delay that yielded the largest aortic VTI at one of eight tested AV intervals (between 60 and 200 ms). New York Heart Association (NYHA) functional classification and quality-of-life (QOL) score were compared 3 months after randomization. RESULTS: Immediately after CRT initiation with AV delay programming, VTI improved by 4.0 +/- 1.7 cm vs 1.8 +/- 3.6 cm (P < .02), and ejection fraction (EF) increased by 7.8 +/- 6.2% vs 3.4 +/- 4.4% (P < .02) in group 1 vs group 2, respectively. After 3 months, NYHA classification improved by 1.0 +/- 0.5 vs 0.4 +/- 0.6 class points (P < .01), and QOL score improved by 23 +/- 13 versus 13 +/- 11 points (P < .03) for group 1 vs group 2, respectively. CONCLUSIONS: Echocardiography-guided AV delay optimization using the aortic Doppler VTI improves clinical outcomes at 3 months compared to an empiric AV delay program of 120 ms.

Atrioventricular Node↗