Joon Ryang Rho

The Cox-Maze III procedure for atrial fibrillation associated with rheumatic mitral valve disease

BACKGROUND The surgical results of the Cox-Maze III procedure (CM-III) for atrial fibrillation (AF) associated with rheumatic mitral valve (MV) disease are not as good as the results from surgery for AF alone. METHODS To assess the efficacy and safety of the CM-III in AF associated with rheumatic MV disease, we retrospectively analyzed 75 patients who underwent the CM-III combined with a rheumatic MV procedure between April 1994 and December 1997. Fourteen cases were reoperations because of prosthetic valve failure. RESULTS Mean aortic cross-clamp (ACC) times and cardiopulmonary bypass (CPB) times were 151+/-43 and 251+/-73 min, respectively. Concomitant procedures were mitral valve replacement (MVR) in 25 patients, MVR and aortic valve replacement (AVR) in 14 patients, MV repair in 10 patients, MVR and tricuspid annuloplasty (TAP) in 6 patients, MVR and AV repair in 3 patients, MVR and coronary artery bypass grafting (CABG) in 2 patients, MVR and AVR and CABG in 1 patient, redo-MVR in 8 patients, redo-MVR and TAP in 4 patients, and redo-MVR and redo-AVR in 2 patients. There were two in-hospital mortalities (2 of 75, 2.7%). Seventy-three survivors were followed for a mean duration of 30+/-13 months (12-56 months). Normal sinus rhythm was restored in 90.4% (66 of 73). Three patients remained in AF and 2 patients were in junctional rhythm. Permanent pacemakers were implanted in 2 patients due to sick sinus syndrome. Right atrial (RA) contractility was demonstrable in 100% (66 of 66) and left atrial (LA) contractility in 62.1% (41 of 66) of the patients in the latest follow-up echocardiography. RA and LA contractilities were restored a mean 69+/-93 and 126+/-136 days after the operation, respectively. LA contractility was restored significantly later at a lower rate than RA contractility in rheumatic MV disease. There were no differences in ACC time, CPB time, incidence of postoperative bleeding complications, and sinus conversion rates between non-redo and redo cases in spite of the significantly longer duration of preoperative AF in redo cases (p<0.05). CONCLUSIONS The CM-III for AF associated with rheumatic MV disease demonstrated a high sinus conversion rate with acceptable operative risk even in cases of reoperation.

Surgical results of patients with a functional single ventricle

OBJECTIVE Overall mortality of the patients with a functional single ventricle is still high, though excellent mid- and long-term results of the modified Fontan procedure have been reported. This study assessed the factors that affect the surgical outcomes mainly in the pre-Fontan stage and performed long-term survival analysis. METHODS Between January 1988 and December 2000, 405 patients with a functional single ventricle underwent surgical interventions and were followed up until June 2001. The mean follow-up period was 74.5+/-69.4 months and 95% of the patients were followed up completely. Their median age was 2.5 months at the time of shunt or pulmonary artery banding (PAB), 8.6 months at BCPS, and 28.6 months at the Fontan operation. The variables of the anatomical lesions with single ventricle physiology, combined abnormalities, surgical pathways leading to the Fontan stage, age at operation, study periods, and type of the Fontan procedure were analyzed. The role of BCPS in the long-term results was evaluated. RESULTS Overall survival after birth was 60.1+/-2.8% at 10 years. In multivariate analysis, complete atrioventricular septal defect-typed lesion, pulmonary venous obstruction, total anomalous pulmonary venous connection, and interruption of aortic arch were risk factors for long-term survival, while pulmonary stenosis was demonstrated as a favorable prognostic factor. In this study, there was no significant survival difference between the early and late study period. Actuarial mortality in the pre-Fontan stage was 41.3% in the non-BCPS group and 16.3% in the BCPS group (P<0.001). The 10-year survival rates of the populations in staged and primary Fontan groups were not significantly different (P=0.24). The long-term survival rate of the atriopulmonary Fontan group was significantly lower than that of lateral tunnel Fontan (60.3+/-6.3% vs. 86.8+/-3.1% at 10 years, P=0.0001). CONCLUSION This study revealed that the overall survival was disappointing and there were still problems that need to be solved in the pre-Fontan stage to improve the overall survival. The role of BCPS was not to contribute to the longer survival after Fontan operation, but to lower mortality in the pre-Fontan stage, which can offer a higher probability to proceed to the Fontan procedure successfully.

Changes in the antioxidative defensive system during open heart operations in humans

It is known that reperfusion of the ischemic myocardium may intensify damage and increase the extent of myocardial necrosis. Oxygen free radicals and their metabolites have been implicated as possible elements in myocardial ischemia-reperfusion injury. In this study in cyanotic patients undergoing open heart operation for tetralogy of Fallot, the myocardial tissue activities of catalase, superoxide dismutase, glutathione peroxidase, and lactate dehydrogenase were determined together with the tissue contents of malondialdehyde, oxidized glutathione, and total glutathione using the spectrophotometric assay method. The tissue activities of catalase, superoxide dismutase, and glutathione peroxidase increased significantly after myocardial reperfusion (p < 0.05) when compared with the tissue activities of the control group (myocardial tissue taken immediately after aortic cross-clamping). The tissue content of malondialdehyde increased significantly after reperfusion (p < 0.05), but the tissue activity of lactate dehydrogenase and the ratio of oxidized glutathione to total glutathione showed an insignificant difference after reperfusion. These data suggest that peroxidation of the cardiac lipids was triggered by the reperfusion of the hypoxic heart, but the myocardial cellular damage was not significant enough to decrease the myocardial lactate dehydrogenase and total glutathione levels. These results also suggest that oxygen free radicals may play an important role in in-vivo myocardial reperfusion stress, but endogenous self-defensive enzyme systems to protect the cell against the cytotoxic oxygen metabolites also were triggered, and the resulting myocardial cellular damage was insignificant.

A moving-actuator type electromechanical total artificial heart. II. Circular type and animal experiment

For pt.I see ibid., vol.37, no.12, p.1186-94 (1990). A novel type of electromechanical total artificial heart (TAH) based on a circular rolling cylinder mechanism was developed to overcome critical problems in motor-driven artificial hearts, such as large size and difficulties in fitting the heart to atrial remnants and arterial vessels. Its performance and reliability were evaluated in mock circulation and in an animal implant experiment. The total weight and volume of the pump are 650 g and 600 mL, respectively. This pump was implanted in a calf for total heart replacement and 96 h of survival was achieved. The whole system, including pump, controller, and control algorithm performed well enough to improve the prospect of eventual clinical application of this TAH system.<<ETX>>

Lecompte procedure for complete transposition of the great arteries with ventricular septal defect and pulmonary stenosis

From December 1988 to February 1993, 19 patients were treated by the Lecompte procedure for complete transposition of the great arteries associated with a ventricular septal defect and pulmonary stenosis. The mean age at operation was 3.1 +/- 0.8 years (mean +/- standard error). This technique consisted of resecting the outlet septum, constructing a tunnel that connected the left ventricle to the aorta, closing the proximal pulmonary arterial stump, pulling the distal pulmonary artery down to the right ventriculotomy site directly, and covering anteriorly with the fixed autologous pericardium. Operative mortality was 5.3%. The mean follow-up was 24.2 +/- 3 months, with no late death. One reoperation was performed because of residual right ventricular outflow tract obstruction. All survivors were studied by echocardiography at intervals of 6 months to 1 year. In all survivors (except for 1 child who underwent reoperation), the estimated pressure gradient between the right ventricle and the pulmonary artery, the structure of the left ventricular outflow tract, left ventricular function, and right ventricular contractility were all satisfactory.

Analysis of the interventricular pressure waveform in the moving-actuator total artificial heart

Right and left filling pressures are important parameters in the automatic control of a total artificial heart (TAH) within normal physiologic ranges. Our TAH is composed of a moving actuator, right and left ventricles, and an interventricular space (IVS) enclosed by a semirigid housing. During operation of the TAH, the IVS volume is changed dynamically by the difference between the ejection volume of one ventricle and the inflow volume of the other. We measured the interventricular pressure (IVP) waveform by using a pressure sensor and analyzed the relationship between the IVP and the preload condition. From in vitro and in vivo experiments, we found that the measured filling pressures were linearly related to the negative peak value of the IVP. Additionally, we found that we could use the time interval from actuator start to the positive peak value of the IVP (outflow valve opening) as a useful parameter to estimate the blood filling volume of the diastole ventricle.

Design of moving-actuator total artificial heart (Korean Heart)

A new version of the moving-actuator electromechanical total artificial heart was designed, to improve total efficiency, durability, and fit inside the thoracic cavity. In contrast to our previous model, with the rolling cylinder actuator, this new model has a pendulum-type actuator with reciprocating motion around a fixed circular path, connected through the gear mechanisms to the motor. By using this mechanism, the efficiency and durability could be improved by replacing the sliding mechanism with rolling contact elements. Also, the height of the pump could be decreased from 9 cm to 7 cm, with a static stroke volume of 65 cc. With this pump, we have performed two animal experiments.

In vivo experiment leading to clinical application of an electrohydraulic ventricular assist device with magnetic coupling.

We developed an electrohydraulic ventricular assist device with magnetic coupling. The integrated system consists of a blood pump, a water conduit for pressure transmission, a bellows type pumping sac, an actuator for transforming the circular motion of a motor to the linear motion of a pusher plate attached to the pumping sac with magnetic coupling, and a controller. The purpose of the coupling was to prevent excessive sucking against the atrial wall. Number 21 Medtronic Hall (Irvine, CA) mechanical valves were used in the inflow and outflow ports of the blood pump. Maximum dynamic stroke volume was 48 ml, and against a mean afterload of 100 mm Hg, maximum pump output was 7 L/min. Chronic in vivo experiments were performed in three sheep, and during these evaluations the system showed no noticeable problems related to mechanical or electronic devices. When left atrial pressure decreased below 0 mm Hg, the magnetic coupling system decoupled the pumping sac and pusher plate with satisfactory reliability. The device was clinically applied in a postoperative patient with chronic dilating cardiomyopathy, and no significant device related problems ensued. These results prove that the electrohydraulic ventricular assist system with magnetic coupling is a suitable ventricular assist device.

An Adaptive Cardiac Output Control for the Total Artificial Heart Using a Self-Tuning Proportional-Integral-Derivative (PID) Controller

The development of a control method for the totally implantable artificial heart (TAH) to regulate cardiac output according to the change in physiological demand was the goal of this study. The conventional proportional-integral-derivative (PID) controller was used for the automatic regulation of the cardiac output. Furthermore, using a fuzzy gain-tuning algorithm, the PID controller parameters were adaptively tuned to the optimal operating point of the process, which varied with hemodynamic disturbances. To determine the physiological demand, the interventricular pressure (IVP) inside the TAH was used to estimate inflow conditions. The negative peak value of the IVP at each diastolic period has a linear relation to the corresponding atrial pressure. Based on the relationship of atrial pressure to the IVP, the automatic control algorithm proposed regulates the optimal pump rate in terms of sufficient cardiac output delivery under a given venous return. To maintain a well-balanced left and right pump output from the volumetrically coupled, circular moving actuator type TAH, the automatic control also adjusts an asymmetric amount of the moving actuator stroke angle, which provides a different net output of the ventricles. The in vitro performance of the newly developed automatic control method was assessed using a mock circulatory system. Over a physiological range of preload, -3–15 mmHg of right atrial pressure (RAP) and 80–120 mmHg of aortic pressure (AoP), the cardiac output varied from 4.2 to 6.31/min with the left atrial pressure (LAP) maintained below 15 mmHg.