Toshinobu Kazui

The impact of 6 weeks of atrial fibrillation on left atrial and ventricular structure and function

OBJECTIVE The impact of prolonged episodes of atrial fibrillation on atrial and ventricular function has been incompletely characterized. The purpose of this study was to investigate the influence of atrial fibrillation on left atrial and ventricular function in a rapid paced porcine model of atrial fibrillation. METHODS A control group of pigs (group 1, n = 8) underwent left atrial and left ventricular conductance catheter studies and fibrosis analysis. A second group (group 2, n = 8) received a baseline cardiac magnetic resonance imaging to characterize left atrial and left ventricular function. The atria were rapidly paced into atrial fibrillation for 6 weeks followed by cardioversion and cardiac magnetic resonance imaging. RESULTS After 6 weeks of atrial fibrillation, left atrial contractility defined by atrial end-systolic pressure-volume relationship slope was significantly lower in group 2 than in group 1 (1.1 ± 0.5 vs 1.7 ± 1.0; P = .041), whereas compliance from the end-diastolic pressure-volume relationship was unchanged (1.5 ± 0.9 vs 1.6 ± 1.3; P = .733). Compared with baseline, atrial fibrillation resulted in a significantly higher contribution of left atrial reservoir volume to stroke volume (32% vs 17%; P = .005) and lower left atrial booster pump volume contribution to stroke volume (19% vs 28%; P = .029). Atrial fibrillation also significantly increased maximum left atrial volume (206 ± 41 mL vs 90 ± 21 mL; P < .001). Left atrial fibrosis in group 2 was significantly higher than in group 1. Atrial fibrillation decreased left ventricular ejection fraction (29% ± 9% vs 58 ± 8%; P < .001), but left ventricular stroke volume was unchanged. CONCLUSIONS In a chronic model of atrial fibrillation, the left atrium demonstrated significant structural remodeling and decreased contractility. These data suggest that early intervention in patients with persistent atrial fibrillation might mitigate against adverse atrial and ventricular structural remodeling.

A novel minimally invasive off-pump biventricular assist device insertion technique

From the Division of Cardiothoracic Surgery, Banner University Medical Center–Tucson, Tucson, Ariz. Disclosures: Authors have nothing to disclose with regard to commercial support. Received for publication April 15, 2015; revisions received June 8, 2015; accepted for publication July 24, 2015; available ahead of print Aug 28, 2015. Address for reprints: Zain Khalpey, MD, PhD, Division of Cardiothoracic Surgery, The University of Arizona Medical Center, 1501 N Campbell Ave, Room 4302A, PO Box 245071, Tucson, AZ 85724-5071 (E-mail: zkhalpey@surgery.arizona.edu). J Thorac Cardiovasc Surg 2016;151:e5-7 0022-5223/

Differential impact of short periods of rapid atrial pacing on left and right atrial mechanical function

36.00 Copyright 2016 by The American Association for Thoracic Surgery http://dx.doi.org/10.1016/j.jtcvs.2015.07.074

Hemolysate-mediated platelet aggregation: an additional risk mechanism contributing to thrombosis of continuous flow ventricular assist devices

Current techniques to describe atrial function are limited by their load dependency and hence do not accurately reflect intrinsic mechanical properties. To assess the impact of atrial fibrillation on atrial function, combined pressure-volume relationships (PVR) measured by conductance catheters were used to evaluate the right (RA) and left (LA) atrium in 12 isoflurane-anesthetized pigs. Biatrial PVR were recorded over a wide range of volumes during transient caval occlusion at baseline sinus rhythm (SR), after onset of rapid atrial pacing (RAP), after 1 h of RAP, after conversion to SR, and after 1 h of recovery. Cardiac output decreased by 16% (P = 0.008) with onset of RAP. Mean LA and RA pressures increased by 21 and 40% (P < 0.001), respectively, and remained elevated during the entire recovery period. RA reservoir function increased from 51 to 58% and significantly dropped to 43% after resumption of SR (P = 0.017). Immediately after RAP, a right shift of LA end-systolic PVR-intercept for end-systolic volume required to generate an atrial end-systolic pressure of 10 mmHg (24.4 ± 4.9 to 28.1 ± 5.2 ml, P = 0.005) indicated impaired contractility compared with baseline. Active LA emptying fraction dropped from 17.6 ± 7.5 to 11.7 ± 3.7% (P < 0.001), LA stroke volume and ΔP/Δt(max)/P declined by 22% (P = 0.038 and 0.026, respectively), while there was only a trend to impaired RA systolic function. Stiffness quantified by the ratio of pressure to volume at end-diastole was increased immediately after RAP only in the RA (P = 0.020), but end-diastolic PVR shifted rightward in both atria (P = 0.011 LA, P = 0.045 RA). These data suggest that even short periods of RAP have a differential impact on RA and LA function, which was sustained for 1 h after conversion to SR.

Minimally invasive approach for percutaneous CentriMag right ventricular assist device support using a single PROTEKDuo Cannula

Despite the clinical success and growth in the utilization of continuous flow ventricular assist devices (cfVADs) for the treatment of advanced heart failure, hemolysis and thrombosis remain major limitations. Inadequate and/or ineffective anticoagulation regimens, combined with high pump speed and non-physiological flow patterns, can result in hemolysis which often is accompanied by pump thrombosis. An unexpected increase in cfVADs thrombosis was reported by multiple major VAD implanting centers in 2014, highlighting the association of hemolysis and a rise in lactate dehydrogenase (LDH) presaging thrombotic events. It is well established that thrombotic complications arise from the abnormal shear stresses generated by cfVADs. What remains unknown is the link between cfVAD-associated hemolysis and pump thrombosis. Can hemolysis of red blood cells (RBCs) contribute to platelet aggregation, thereby, facilitating prothrombotic complications in cfVADs? Herein, we examine the effect of RBC-hemolysate and selected major constituents, i.e., lactate dehydrogenase (LDH) and plasma free hemoglobin (pHb) on platelet aggregation, utilizing electrical resistance aggregometry. Our hypothesis is that elements of RBCs, released as a result of shear-mediated hemolysis, will contribute to platelet aggregation. We show that RBC hemolysate and pHb, but not LDH, are direct contributors to platelet aggregation, posing an additional risk mechanism for cfVAD thrombosis.

Impact of differential right-to-left shunting on systemic perfusion in pulmonary arterial hypertension

BackgroundRight ventricular failure is a serious complication after left ventricular assist device placement.Case PresentationA 70-year-old male in decompensated heart failure with right ventricular failure after the placement of a left ventricular assist device. A single dual-lumen PROTEKDuo cannula was inserted percutaneously via the internal jugular vein to draw blood from the right atrium and return into the pulmonary artery using the CentriMag system, by passing the failing ventricle. The patient was successfully weaned from right ventricular assist device.ConclusionsIn comparison to two-cannula conventional procedures, this right ventrivular assist device system improves patient rehabilitation and minimizes blood loss and risk of infection, while shortening procedure time and improving clinical outcomes in right ventricular failure.

Changes in left ventricular twist after mitral valve repair.

This study aimed at identifying the ideal right‐to‐left shunt‐fraction to improve cardiac output (CO) and systemic perfusion in pulmonary arterial hypertension (PHT).

Aortic Valve Myxoma Mimicking Vegetation: Report of a Case

OBJECTIVE We performed echocardiographic tissue tracking to investigate whether mitral valve repair preserves left ventricular function. METHODS We studied 16 subjects without heart disease (11 male; mean age, 54.6 ± 15.1 years) and 18 patients in normal sinus rhythm undergoing solitary mitral valve repair (12 male; mean age, 53.6 ± 16.6 years). Transthoracic echocardiography was performed before and after surgery, and left ventricular apical and basal short-axis images were recorded. Left ventricular rotation angle was measured with off-line Vector Velocity Imaging (Siemens Medical Solutions USA Inc, Mountain View, Calif) at each slice level. RESULTS Left ventricular ejection fraction was significantly higher in the control (68.4% ± 3.6%) and preoperative groups (70.9% ± 6.5%) than the postoperative group (59.4% ± 11.4%, P < .05). Left ventricular end-diastolic and end-systolic volumes were significantly greater in the preoperative group than the control group (130.0 ± 41.5 mL and 41.6 ± 16.6 mL vs 80.0 ± 16.7 mL and 26.6 ± 9.2 mL, respectively, P < .05). Left ventricular end-diastolic volume normalized postoperatively. Left ventricular twist was significantly greater in the preoperative group than the other groups (11.7° ± 4.1° versus 7.1° ± 3.8° and 8.2° ± 5.7°, P < .05). Left ventricular twist did not differ significantly between control and postoperative groups. New York Heart Association functional class improved from 1.6 ± 0.5 to 1.0 ± 0.0 after surgery (P < .05). CONCLUSIONS Although preoperative left ventricular ejection fraction seemed normal, left ventricular twist was greater. Left ventricular twist normalized after surgery, suggesting that it preserves left ventricular function.

Epicardial Ablation Performance of a Novel Radiofrequency Device on the Beating Heart in Pigs

We report a case of cardiac myxoma of the aortic valve. To our knowledge, this represents only the seventh such case ever documented. A 61-year-old woman underwent an echocardiography to screen for hypertensive–diabetic cardiac complications, which showed a mass on her aortic valve. Although she had not experienced a fever, the mass closely resembled a vegetation, resulting in an initial diagnosis of infective endocarditis. We extirpated the mass and repaired the aortic valve with the patient under cardiopulmonary bypass. The postoperative course was uneventful. Histological examination confirmed that the mass was a myxoma.

Combined Aortic and Mitral Valve Repair

PURPOSE Only bipolar clamps create reliable transmural lesions on the beating heart. This study evaluated the performance of a new radiofrequency (RF) device on the beating heart in an acute porcine model. DESCRIPTION Six domestic pigs were ablated with a novel bipolar RF linear device on the beating heart (ablation time of 40 s, 3 each on right and left atria and 1 each on superior and inferior vena cavae). The heart was stained with 2, 3, 5-triphenyl-tetrazolium chloride, and each lesion was cross-sectioned for lesion depth and transmurality. EVALUATION Transmurality was documented in 89% of the cross-sections. Sixty-three percent of lesions were transmural along the entire lesion length. Overall, 85% of the nontransmural cross-sections were located on the right atrium, and half of the nontransmural sections were in the superior or inferior vena cavae lesions. CONCLUSIONS This novel device was able to create transmural lesions on the beating heart, more effectively in the left atrium than in the right atrium.