Minako Katayama

Impact of pericardial adhesions on diastolic function as assessed by vortex formation time, a parameter of transmitral flow efficiency

BackgroundPericardial adhesions are a pathophysiological marker of constrictive pericarditis (CP), which impairs cardiac filling by limiting the total cardiac volume compliance and diastolic filling function. We studied diastolic transmitral flow efficiency as a new parameter of filling function in a pericardial adhesion animal model. We hypothesized that vortex formation time (VFT), an index of optimal efficient diastolic transmitral flow, is altered by patchy pericardial-epicardial adhesions.MethodsIn 8 open-chest pigs, the heart was exposed while preserving the pericardium. We experimentally simulated early pericardial constriction and patchy adhesions by instilling instant glue into the pericardial space and using pericardial-epicardial stitches. We studied left ventricular (LV) function and characterized intraventricular blood flow with conventional and Doppler echocardiography at baseline and following the experimental intervention.ResultsSignificant decreases in end-diastolic volume, ejection fraction, stroke volume, and late diastolic filling velocity reflected the effects of the pericardial adhesions. The mean VFT value decreased from 3.61 ± 0.47 to 2.26 ± 0.45 (P = 0.0002). Hemodynamic variables indicated the inhibiting effect of pericardial adhesion on both contraction (decrease in systolic blood pressure and +dP/dt decreased) and relaxation (decrease in the magnitude of -dP/dt and prolongation of Tau) function.ConclusionPatchy pericardial adhesions not only negatively impact LV mechanical functioning but the decrease of VFT from normal to suboptimal value suggests impairment of transmitral flow efficiency.

Accurate guidance of a catheter by ultrasound imaging and identification of a catheter tip by pulsed-wave Doppler.

Background:  With the advent of numerous minimally invasive medical procedures, accurate catheter guidance has become imperative. We introduce and test an approach for catheter guidance by ultrasound imaging and pulsed‐wave (PW) Doppler.

Visual Estimation of the Severity of Aortic Stenosis and the Calcium Burden by 2-Dimensional Echocardiography: Is It Reliable?

Guidelines have recommended aortic valve surgery in asymptomatic patients with severe aortic stenosis and a large aortic valve calcium burden. The purpose of this study was to determine whether visual assessment of aortic valve calcium and stenosis severity are reliable based on 2‐dimensional echocardiography alone.

Predictors of Elevated Cardiac Enzyme Levels in Hospitalized Patients with Atrial Fibrillation and No Known Coronary Artery Disease

We retrospectively studied the predictive capabilities of elevated cardiac enzyme levels in terms of the prognosis of patients who were hospitalized with atrial fibrillation and who had no known coronary artery disease. Among 321 patients with atrial fibrillation, 60 without known coronary artery disease had their cardiac enzyme concentrations measured during hospitalization and underwent stress testing or cardiac catheterization within 12 months before or after hospitalization. We then compared the clinical and electrocardiographic characteristics of the 20 patients who had elevated cardiac enzyme levels and the 40 patients who had normal levels. Age, sex, and comorbidities did not differ between the groups. In the patients with elevated cardiac enzyme levels, the mean concentrations of troponin T and creatine kinase-MB isoenzymes were 0.08 ± 0.08 ng/mL and 6.49 ± 4.94 ng/mL, respectively. In univariate analyses, only peak heart rate during atrial tachyarrhythmia was predictive of elevated enzyme levels (P <0.0001). Mean heart rate was higher in the elevated-level patients (146 ± 22 vs 117 ± 29 beats/min; P=0.0007). Upon multivariate analysis, heart rate was the only independent predictor of elevated levels. Coronary artery disease was found in only 2 patients who had elevated levels and in one patient who had normal levels (P=0.26). Increased myocardial demand is probably why the presenting heart rate was predictive of elevated cardiac enzyme levels. Most patients with elevated enzyme levels did not have coronary artery disease, and none died of cardiac causes during the 6-month follow-up period. To validate our findings, larger studies are warranted.

Does valvuloarterial impedance impact prognosis after surgery for severe aortic stenosis in the elderly

Background Valvuloarterial impedance (Zva) was introduced as a prognostic measure in patients with aortic stenosis (AS). However, it is unclear whether Zva has a prognostic impact on survival after surgical aortic valve replacement (AVR) in patients with severe AS with preserved ejection fraction (EF). Methods We retrospectively reviewed 929 consecutive patients who had AVR. We investigated 170 elderly patients (age >65 years, mean 76 years) who had AVR secondary to severe AS (mean gradient ≥40 mm Hg; aortic valve area ≤1 cm2; peak velocity ≥4 m/s). Patients with EF <50%, greater than moderate aortic regurgitation, prior heart surgery and concomitant mitral or tricuspid valve surgery were excluded. Zva was calculated and the patients were divided into two groups; low Zva, Zva <4.3 (n=82) and high Zva, Zva ≥4.3 (n=88). The end point was all-cause of death. Survival curves were calculated according to Kaplan-Meier method. Results Age, prevalence of hypertension, diabetes, chronic kidney disease (CKD), atrial fibrillation, symptoms, EF, E/e′ and concomitant coronary artery bypass graft were not different between the groups. Survival was not different between the groups at 5 years (70% in low Zva and 81% in high Zva; p=0.21) and for the entire follow-up period (p=0.23). Only age was a significant factor in predicting survival by multivariate analyses in Cox proportional hazards model after adjusting for Zva, CKD, atrial fibrillation and hypertension. Conclusions Our results suggest that preoperative Zva does not have a prognostic impact on postoperative survival in elderly patients with severe AS with preserved EF. Further investigation is needed to elucidate the controversial results.

Detection of Progressive Myocardial Tissue Injury by Ultrasonic Integrated Backscatter Immediately After Coronary Reperfusion

Myocardial reperfusion following ischemia may paradoxically cause additional injury, including microvascular damage and edema. These structural alterations augment tissue echogenicity, which is measurable by ultrasonic integrated backscatter (IB). We sought to characterize alterations in myocardial IB in an ischemic and reperfused region of the rat heart. Myocardial IB of the regions of interest in 12 adult male Sprague-Dawley rats was studied at baseline, during ischemia, and chronologically after coronary reopening, using an ultrasound frequency of 8 MHz. IB did not significantly change between baseline and ischemia. However, within 1 min of reperfusion, IB significantly increased and continued to increase until 10 min of reperfusion, when a plateau was reached. Areas of high echogenicity were comparable to infarcted areas on gross pathologic slices and had edema with extravasation of red blood cells. Myocardial reperfusion following ischemia significantly augments tissue echogenicity. A continuing increase of IB suggests a rapid progression of reperfusion injury.

An Interposed Pad in Open-Chest Echocardiographic Porcine Scans for Mimicking Ultrasound Signal Attenuation in a Human Chest: A Pad for Mimicking Human Chest Attenuation

Opening a chest in an experimental echocardiographic animal study eliminates ultrasound signal attenuation by the chest wall. We developed a scanning technique that involves the use of an attenuative pad created from a mixture of urethane and titanium dioxide. The pad was interposed within transmission gel between the transducer face and cardiac surface in open‐chest scans in a porcine model. Comparative measurements of left ventricular echogenicity without and with the pad demonstrate that the pad reproducibly causes ultrasound signal attenuation that closely mimics chest attenuation in clinical transthoracic echocardiographic studies.

Left Ventricular Septal Hypertrophy in Elderly Patients With Aortic Stenosis

Left ventricular (LV) septal hypertrophy in aortic stenosis raises diagnostic and therapeutic questions. However, the etiology and clinical consequences of this finding have not been well studied. The aim of this study was to perform a morphologic evaluation of the LV in aortic stenosis and to investigate the contributing factors and consequences of septal hypertrophy.

Optimized administration regimen of lopinavir for a myocardial ischaemia reperfusion study in Sprague–Dawley rats

Pharmacokinetics of drugs may differ between small and large mammals (including humans); therefore, drug testing in animal models must be carefully designed. Sprague–Dawley rats were used in cardiac experiments, during which the lopinavir concentration in serum had to match human therapeutic levels (4–10 μg/mL). Lopinavir was administered as a co-formulated drug of lopinavir and ritonavir. It was found that after a single administration of a standard human peroral dose (lopinavir 13.3 mg/kg of body weight), the serum concentration of lopinavir was only one-tenth of the target level. It remained below the minimum target level even after 10-fold the standard dose was administered. After initial pilot tests, a dose escalation study was conducted with oral doses 10- and 15-fold the standard clinical dose of lopinavir (i.e. 133 and 200 mg/kg, respectively). A second administration 2 h later effectively increased and maintained higher concentrations during the experimental ischaemia and reperfusion periods. A dose-dependent increase in serum concentration of the drug was observed. Thus, the target therapeutic serum level of lopinavir in the rats was achieved by administrating 10- to 15-fold the standard human dose twice, separated by a 2 h interval.