Katayama, Minako

Background: Myocardial reperfusion following prolonged ischemia may paradoxically cause additional injury, including edema and microvascular damage. These structural alterations augment tissue echogenicity measurable by integrated backscatter (IB). We sought to characterize alterations of myocardial IB in an ischemic and then reperfused region of the rat heart. Methods: Myocardial IB in 12 adult male Sprague-Dawley rats was studied at baseline, 60 minutes after left anterior descending coronary artery occlusion, and chronologically after coronary reopening. Short-axis scans of the mid left ventricle were acquired at a frequency of 8 MHz. Mean±SD values of IB were measured in the region of interest at baseline, ischemia, and reperfusion, and assessed by a paired t-test. Results: See figure and table. IB did not significantly change between baseline and ischemia. However, within 1 minute of reperfusion, IB significantly increased, as compared to both baseline and ischemia, and continued to increase until 10 minutes after reperfusion, when a plateau was reached. Conclusions: Myocardial reperfusion following acute prolonged ischemia in a rat heart significantly augments tissue echogenicity. A continuing increase of IB within minutes of the reperfusion onset and the subsequent plateau of elevated IB values suggest progression and completion, respectively, of reperfusion injury, detectable by a high-frequency transducer.

Percutaneous transendocardial injections of therapeutic agents into the myocardium may not always be effective. We used an animal model for assessing the efficacy of the injections using linoleic acid as a testing agent. Efficacious delivery into the myocardium of a beating heart was indicated by rapidly developed local myocardial necrosis and wall motion abnormalities using echocardiography. We employed this experimental model to test our innovative technology, an acoustically active injection catheter. The Doppler ultrasound‐guided acoustically active injection catheter effectively delivers the substance to the myocardium but needs further technical improvements to minimize an unwanted systemic distribution of the agent.

An 85-year-old man with cardiac history notable for atrial fibrillation diagnosed 10 years ago which was being treated with atenolol and warfarin presented to our institution with persistent atrial fibrillation. His echocardiogram showed ejection fraction (EF) of 56%, no regional wall motion abnormalities, mild mitral and pulmonary regurgitation, and trivial tricuspid regurgitation. Despite this treatment, he had recurrent episodes of paroxysmal symptomatic atrial fibrillation with a rapid rate requiring multiple emergency department visits and hospital admissions. Given difficulty to control the rate, he underwent atrioventricular (AV) nodal ablation and leadless pacemaker insertion. Fifteen days after the procedure, he was found to have a severe mitral regurgitation murmur.

B‐mode ultrasound imaging guidance of cannulas can be compromised by noise, artifacts, and echogenicity that is not distinctive from that of surrounding anatomy. We have modified a venovenous extracorporeal membrane oxygenation cannula by embedding piezoelectric crystals into each of its 3 blood flow ports. Each vibrating crystal acoustically interacts with a Doppler imaging signal and produces an instantaneous color marker. The aim of this study was to compare identification of the extracorporeal membrane oxygenation cannula ports by B‐mode imaging versus the color Doppler marker. Unlike B‐mode imaging, the color Doppler marker identified the corresponding port even in highly challenging closed‐chest scans in anesthetized pigs. The method could improve guidance accuracy of cannulas by ultrasound scans.

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.

ObjectivesLeft 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.MethodsPatients with moderate or severe aortic stenosis were prospectively enrolled. Patients with previous myocardial infarction, wall motion abnormalities, at least moderate valvular regurgitation, known cardiomyopathy, an LV ejection fraction of less than 50%, and age younger than 65 years were excluded.ResultsForty‐one patients underwent a final analysis. Septal hypertrophy (LV septal wall thickness ≥15 mm) was confirmed in 21 of 41 patients. The septal hypertrophy group had higher peak aortic valve velocity, a higher diabetes mellitus rate, and a higher rate and longer duration of hypertension than those without septal hypertrophy. The peak aortic valve velocity (odds ratio, 7.1; 95% confidence interval, 1.4–37.1) and diabetes mellitus (odds ratio, 7.4; 95% confidence interval, 1.2–46.2) were the significant factors associated with septal hypertrophy by multivariate analysis. Intraventricular conduction disturbance on electrocardiography was more frequent in the septal hypertrophy group (P = .021).ConclusionsLeft ventricular septal hypertrophy was commonly observed in elderly patients with aortic stenosis, and a higher aortic valve velocity, hypertension, and diabetes mellitus were associated factors. Intraventricular conduction disturbance occurred more often in patients with septal hypertrophy than those without, which implies the pathophysiologic consequence. Further studies are needed to determine the impact of septal hypertrophy and intraventricular conduction disturbance on the prognosis of patients after aortic valve interventions.

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.

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.