Biomedical subjects

Victor G Davila-Roman

Publications and source records attributed to Victor G Davila-Roman.

5 recordsLinked to original sources

PubMed2005

The effects of plasma insulin and glucose on myocardial blood flow in patients with type 1 diabetes mellitus.

OBJECTIVES: The objective of this study was to determine the impact of insulin and glucose on myocardial vasodilator function in patients with type 1 diabetes mellitus (T1DM). BACKGROUND: The relative importance of plasma insulin and glucose levels on the abnormal vasodilator function observed in T1DM is unknown. METHODS: Twenty T1DM patients underwent positron emission tomography studies to measure myocardial blood flow (MBF) (in ml/g/min) at rest (MBFr) and during adenosine (MBFa), both under baseline metabolic conditions and then during either hyperinsulinemic-euglycemic clamp (HE) (n = 10; 40 +/- 9 years, 8 female subjects, hemoglobin A1c [HbA1c] 7.8 +/- 1.1%) or hyperinsulinemic-hyperglycemic clamp (HH) (n = 10; 44 +/- 12 years, 8 female subjects, hemoglobin A1c 7.7 +/- 0.6%). RESULTS: Both groups showed similar MBFr and MBFa under baseline metabolic conditions (p = NS). Compared with baseline conditions, MBFr increased in the HH group (p < 0.005), whereas it did not change in the HE group. Compared with baseline conditions, MBFa decreased in the HH group (p < 0.05) but did not change in the HE group. Myocardial perfusion reserve (MPR) (MBFa/MBFr) was similar between the HE and HH groups at baseline (p = NS). During clamp, MPR tended to decrease in the HH group (p < 0.1) but did not change in the HE group (p = NS) when compared with baseline conditions. However, during the clamp MPR was significantly lower in the HH group when compared with the HE group (p < 0.0001). CONCLUSIONS: In the short term, hyperglycemia has a deleterious effect on myocardial vasodilator function, which outweighs the beneficial effect of hyperinsulinemia.

Adult↗

PubMed2005

Myocardial systolic strain is decreased after aortic valve replacement in patients with aortic insufficiency.

BACKGROUND: Left ventricular three-dimensional nonlinear systolic strain determinations have potential to detect small decrements in ventricular function in patients with aortic insufficiency before and after aortic valve replacement. METHODS: Magnetic resonance imaging with tissue-tagging was performed on 42 normal volunteers and 14 patients with chronic aortic insufficiency both before and 28 +/- 11 months after aortic valve replacement. Preoperative and postoperative left ventricular volume, dimensions and ejection fraction were determined for all subjects. Left ventricular systolic radial, circumferential, longitudinal, and minimum principal strain were calculated for six left ventricular regions. RESULTS: After aortic valve replacement, left ventricular volume and dimensions decreased significantly (p < 0.001) and ejection fraction increased nonsignificantly (p = 0.096). Strain values in preoperative aortic insufficiency patients did not differ significantly from controls. At an average of 28 +/- 11 months postoperatively, however, regional three-dimensional minimum principal and longitudinal strain was decreased in all six ventricular regions as well as globally (p < 0.03) compared with normal control values. Circumferential strain was significantly decreased globally and in all but two regions (p < 0.03). CONCLUSIONS: These magnetic resonance imaging-based techniques are sensitive enough to detect a previously unrecognized, significant decrease in both global and regional three-dimensional left ventricular systolic strain 2 years after aortic valve replacement for minimally symptomatic chronic aortic insufficiency despite improvement in ejection fraction and a decrease in left ventricular size. The reasons for a significant decline in left ventricular systolic strain after successful aortic valve replacement in minimally symptomatic chronic aortic insufficiency patients are not clear and warrant further investigation.

Adult↗

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↗

PubMed2003

Severe aortic insufficiency and normal systolic function: determining regional left ventricular wall stress by finite-element analysis.

BACKGROUND: Because severe aortic insufficiency in the setting of preserved left ventricular function is often associated with a long asymptomatic period and unpredictable course on medical therapy, sensitive indices of left ventricular systolic performance are necessary for the optimal direction of therapeutic intervention. Because myocardial wall stress is closely related to both pathologic cardiac remodeling and ultimately to left ventricular decompensation, an accurate description of regional wall stress distribution may improve our ability to clinically manage these patients appropriately. The objectives of this study were (1) to define sensitive, noninvasive indices of left ventricular systolic performance to assist the clinician in the serial evaluation and early detection of increased left ventricular wall stress and, therefore, inadequate left ventricular remodeling and subsequent myocardial decompensation of patients with aortic insufficiency, and (2) to quantify differences in instantaneous global and regional end-systolic wall stress between normal subjects and patients. METHODS: Magnetic resonance imaging was performed on 23 normal volunteers and 19 patients with aortic insufficiency and normal systolic function (ejection fraction, 57% +/- 6%). Finite-element analysis was used to estimate global and regional end-systolic stress. RESULTS: End-systolic stress was significantly higher in the patient group globally (154,700 +/- 31,711 versus 96,781 +/- 23,185 dyne/cm(2); p < 0.001) and regionally (p < 0.001 in all segments) despite normal systolic function and similar end-systolic pressures. CONCLUSIONS: End-systolic stress as determined by magnetic resonance imaging and finite-element analysis may have considerable potential as a noninvasive, clinically applicable index of regional left ventricular function that may help in the serial evaluation, optimal management, and early identification of left ventricular decompensation in patients with aortic insufficiency.

Adult↗

PubMedDate not supplied

Aortic valve replacement for aortic insufficiency: valve type as a determinant of systolic strain recovery.

BACKGROUND AND AIM: Left ventricular (LV) 3D systolic strain decreases in absolute value postoperatively and does not recover in patients who undergo aortic valve replacement (AVR) for chronic aortic insufficiency (AI). We investigated whether choice of valve prosthesis (mechanical [St. Jude], bioprosthetic [bovine pericardial], Ross procedure) had a significant impact on strain recovery in this surgical population. METHODS: MRI with tissue-tagging was performed on 14 patients with chronic AI both before and 28 +/- 13 months after AVR. Average values of LV systolic strain and end-systolic stress (ESS) were computed from MRI data for the LV. Three types of prosthetic valve were examined (Ross procedure n = 4, bovine pericardial n = 5, and St. Jude n = 5). RESULTS: Overall, systolic strain, ESS, LV volumes, ejection fraction, and LV mass all changed significantly following AVR. Comparisons between individual valve types revealed no differences in any of these measurements. Patients who received a mechanical valve had a greater decrease in the absolute value of systolic strain following surgery compared to patients from the nonmechanical group (Ross procedure and bioprosthetic valve). Comparisons between the Ross group and the prosthetic group (St. Jude and bioprosthetic) produced no significant differences in strain, ESS, LV volume, and mass. CONCLUSIONS: These early results suggest that valve prosthetic type may be a factor in efforts to improve strain recovery after AVR for AI, although further investigation is warranted. MRI with tissue-tagging may be a useful tool for comparing the impact of prosthetic valve choice on incompletely recovered systolic strain following AVR for chronic AI.

Adult↗