Shigenobu M

Evaluation of St. Jude Medical Mitral Valve Function by Exercise Doppler Echocardiography

ABSTRACT The aim of this study was to detect borderline mitral valve dysfunction in 100 asymptomatic patients with a St. Jude Medical valve. We studied rest and exercise hemodynamics by Doppler echocardiography. Study patients were divided into two groups according to the time since surgery: group A had valves implanted less than 5 years ago (44 patients), group B had valves implanted more than 5 years ago (56 patients). Although patients had no clinical signs of valve dysfunction, group B was found to have significant reduction of mitral valve area (p < 0.05). In the group A patients, mean gradients at rest increased from 4 ± 2, 4 ± 2, and 3 ± 1 mmHg in valve sizes of 25, 27, and 29 mm, respectively, to 7 ± 2, 7 ± 3, and 5 ± 2 mmHg with exercise. In the group B patients, mean gradients at rest increased from 7 ± 1, 6 ± 2, and 5 ± 1 mmHg to 14 ± 3, 13 ± 3, and 10 ± 4 mmHg, respectively, after exercise. The percent increase (mean) in peak pressure gradient with exercise was significantly higher in group B (more than 100%) than in group A (less than 80%) (p < 0.01). The percent increase in mean gradient with exercise was also significantly higher in group B (more than 100%) than in group A (less than 75%). In conclusion, patients with reduced valve area and more than a 100% increase of peak and mean gradients should be followed up carefully. If any signs or symptoms of heart failure develop, they must be considered as candidates for surgery.

The effect of myocardial preservation technique on supraventricular tachycardia following aortic valve replacement

We studied 100 patients who underwent an isolated aortic valve replacement (AVR) between 1974 and 1991. The patients were divided into the following two groups and compared: group A, which consisted of 40 patients operated on before 1978 who underwent continuous left coronary perfusion with blood; and group B, which consisted of 60 patients operated on after 1979 in whom St. Thomas solution was used in combination with topical cardiac cooling. Moreover, we divided the group B patients into two subgroups: group Bl, who underwent AVR before 1986 during which we administered St. Thomas solution with ice slush every 30 min; and group B2, who had AVR after 1986 in which we used St. Thomas solution with a cold saline (4°C) solution and treated with a small amount of slushed ice every 15 min. The incidence of supraventricular tachycardias was 15% in group A, 50% in group BI, and 15% in group B2. The severity of preoperative New York Heart Association (NYHA) functional class, the type of valve lesions, cardiothoracic ratio, left ventricular function, aortic clamp time, bypass time, and use of drugs did not correlate with the incidence of supraventricular tachycardias in either group A or B. In group B2 patients, we paid a lot of attention to cooling the right atrium as well as the left ventricle by immersing the whole heart using a 4°C saline solution, which led to a remarkable reduction of the incidence of supraventricular tachycardia. This fact indicates that right atrial preservation is one of the most important factors for reducing the incidence of supraventricular tachycardia.

The clinical and pathological features of isolated aortic regurgitation in relation to its etiology

Chronic isolated aortic regurgitation (AR) caused by degenerative, rheumatic, and Marfan etiologies were compared in a study of 87 patients. There were three hospital deaths in the Marfan group, but none in the rheumatic and degenerative groups. The late postoperative survival rates at 5 and 10 years were 98 % and 94 %, respectively, in the rheumatic group; 84% and 84%, respectively, in the degenerative group; and 85% and 78%, respectively, in the Marfan group. An analysis of the late complications disclosed a higher incidence of aortic dissection and paravalvular leakage in the degenerative and Marfan groups than in the rheumatic group. In the degenerative group, 4 of the 32 patients developed acute aortic dissection within 3 years following aortic valve replacement. The aortic root diameter in these 4 patients was more than 40 mmat the time of surgery, hereas it was less than 40 mm in the remaining 28 patients. In conclusion, considering the progressive nature of myxomatous degeneration, patients with a severely dilated aortic root diameter should be monitored carefully with echocardiography after surgery.

Surgery for Degenerative Mitral Regurgitation Valve Repair v. Valve Replacement with Chordal Preservation

This study compares mitral valve repair and mitral valve replacement with chordal preservation for chronic mitral regurgitation due to myxomatous degeneration with special reference to left ventricular function. Twenty-six patients underwent complete preoperative and 2 years later postoperative echocardiography study. Thirteen patients underwent mitral valve replacement associated with preservation of chordae tendineae and papillary muscles, and 13 patients had mitral valve repair. There were no statistically significant differences between the 2 groups for clinical findings, hemodynamic profiles, or left ventricular function compared prior to surgery. After correcting mitral regurgitation, increase in cardiac index was significant for the repair group. Left ventricular end-diastolic volume decreased in both groups. Left ventricular end-systolic volume significantly decreased in the repair group, but remained unchanged in the replacement group. Both ejection fraction and mean left ventricular circumferential fiber shortening velocity (mVcf) decreased in the replacement group, but significantly increased in the repair group 2 years after surgery. These findings suggest valve replacement with chordal preservation shows less improvement in ventricular systolic function late after surgery compared with mitral valve repair.

Detection of Björk-Shiley Mitral Valve Dysfunction via Doppler Echocardiography

Fifty-eight patients with a Björk-Shiley (B-S) mitral valve were examined to study applicability of Doppler echocardiography in diagnosing and predicting the severity of prosthetic valve dysfunction. The effect of valve replacement on the hemodynamic performance at rest and during bicycle exercise was determined from serial echocardiographic data. The high pressure gradient group in which peak pressure gradients were assumed to be more than 15mmHg at rest, showed negative values of percent change in both stroke volume index (%ΔSVI) and left ventricular end-diastolic volume index (%ΔEDVI). All patients with high pressure gradients had poor exercise response of the left ventricle, whereas most patients with low pressure gradients showed good exercise response. The high pressure gradient group had significantly smaller mitral valve area than did the low pressure group. This suggests that impairment of inflow caused by the artificial valve, namely, prosthetic valve stenosis, is possibly a significant factor causing left ventricular dysfunction—notably a decrease in stroke volume during exercise. Reoperation was performed with good results in 5 of 58 patients because of high pressure gradients across the mitral valve prosthesis caused by tissue overgrowth. We conclude the high pressure gradient group is considered to be a reserved cohort of reoperation and periodical measurement of the pressure gradient via Doppler echocardiography can predict prosthetic valve dysfunction before it deteriorates significantly.

Intermittently stuck occluder: Case report of an unusual complication with the use of an aortic Omniscience prosthesis

SummaryAn occluder which intermittently became stuck in the open position with concomitant aortic regurgitation was encountered in a patient subjected to an aortic valve replacement with a 23 Omniscience prosthetic valve. The patient was intermittently aware of the complete momentary disappearances of the valve sounds, the etiology of which could not be discerned. During fluoroscopic examination, the occluder became stuck for a few cardiac cycles in what appeared to be the fully open position before finally moving. Prosthetic valve malfunction was thus diagnosed.The emergency operation was successful. Operative findings revealed that a thin thrombus had developed in a curtain-like fashion on the left ventricular face of the prosthesis with mild tissue overgrowth along the perimeter of the valve. The Omniscience prosthesis was replaced with a 19-mm St. Jude Medical prosthesis, and the patients post-operative course has been uneventful.