Analog simulation of aortic and of mitral regurgitation.

By using an equivalent electronic circuit either mitral or aortic regurgitation was simulated. Simulation allowed not only a measurement of various pressures within the cardiovascular system and cardiac output, but also mitral and aortic flow. In normal conditions mitral and aortic flows were monophasic, anterograde. In valve regurgitation mitral and aortic flows were, as expected, biphasic. In mitral regurgitation, during systole and diastole the valve flow was retrograde and anterograde, respectively. In aortic regurgitation, during systole and diastole the valve flow was anterograde and retrograde, respectively. The magnitude of the regurgitant valve flow was measured by time-integration and compared to the net flow, i.e. cardiac output. Valve flow was determined not only by the magnitude of valve dysfunction, but also by the resistive/capacitive characteristics of the "falsely" attached regurgitant circuit. If the regurgitant valve flow was large enough, it in turn affected the function of the left ventricle. The present investigation suggests that many features observed in patients with mitral or aortic regurgitation can be qualitatively satisfactorily simulated. In some respects even quantitative simulation is possible. However, for simulation of chronic mitral or aortic regurgitation, in the analog electronic circuit additional adjustments-in capacitance of the left ventricle and pulmonary system--would be required.

Analog simulation of two clinical conditions: (1) acute left ventricle failure; (2) exercise in patient with aortic stenosis.

A computer analysis of an equivalent electronic circuit is developed. Thus it is possible to simulate the human cardiovascular system, its negative feedback loops (including the control of venous tone, of myocardial contractility, and of heart rate) and negative intrathoracic pressure. If the simulated cardiovascular system is acted upon by various disturbances their consequences can be studied in detail. The consequences of two disturbances are studied by simulation: (i) acute left ventricular failure and (ii) exercise (decreased peripheral resistance) in aortic stenosis. However, prior to the simulation of the latter, a relatively complex condition, two additional procedures are implemented, i.e. simulations of (iii) increased sympathetic tone and of (iv) aortic stenosis are performed. Simulation of exercise (decreased peripheral resistance) in aortic stenosis is also compared with data observed in patients. Results show that, by using the present equivalent circuit, conditions described above can be qualitatively and to some extent quantitatively well simulated.

Repetitive paroxysms of supraventricular tachyarrhythmias triggered during pediatric cardiac interventions: suppression after short infusion of amiodarone.

Arrhythmias are the most common major complications encountered during pediatric cardiac catheterizations. This report describes the management of repetitive paroxysms of supraventricular tachyarrhythmias triggered by catheter manipulation during interventional procedures in two children. After 15 minutes, amiodarone infusion (25 microg/kg/min) eliminated further paroxysms in both patients, allowing both interventions to be completed safely and effectively.

Simulation of some short-term control mechanisms in cardiovascular physiology.

The equivalent electronic circuit, developed to simulate cardiovascular physiology, is upgraded to incorporate negative feedback loops. In this way homeostasis of the arterial pressure is simulated in exercise, in haemorrhage, in the insufficiency of the aortic valve, and in hypervolemia. The results show that homeostasis supports the cardiovascular system by modulating Starling mechanism(s) in exercise, haemorrhage and hypervolemia. In aortic insufficiency it seems that only Starling mechanism(s) can maintain cardiac output and arterial pressure.

Is a learning curve for arterial switch operation in small countries still acceptable? Model for cooperation in Europe.

OBJECTIVES: To assess the results of a cooperative arrangement between Slovakia and Slovenia for neonatal cardiac surgery. The aim of the study was to analyze the performance of this approach for complete transposition of the great arteries (D-TGA). METHODS: Due to the overall small number of new patients with D-TGA in Slovenia a decision was made to avoid a prolonged learning curve by centralizing the experience of two countries at one center. Since 1995 the center in Slovakia has become the only referral center for Slovenia. Between February 1993 and June 2002 in this center, 147 patients with D-TGA underwent arterial switch operation (ASO). The median age at operation was 11 days, with 110 patients from Slovakia and 37 patients from Slovenia. RESULTS: Overall hospital mortality was 4.8% (seven patients). The 1, 2, 3, 4 and 5 year survival rate was 95% with the mean follow-up of 4 years. Operation before 1997 (P=0.0001) was identified as a risk predictor for death by multivariate analysis. There are no deaths among the 90 patients operated on after 1996. All patients are without medication with normal left ventricular function. Stenosis (gradient >30 mmHg) was noted in the pulmonary artery reconstruction in seven patients (5%). More than mild aortic regurgitation was noted in five patients (4%). The incidence of redo or reintervention was 5% at 5 years of follow-up. CONCLUSIONS: In the current era a prolonged learning curve for ASO is not acceptable to most European countries and their patients. The risk of surgery can be minimized by concentrating surgical experience as part of the quality control of congenital heart programs. If the number of new patients is small due to the birth rate and size of the population, institutions should merge activity. Such centralization amplifies the experience to the benefit of the patient.

Successful outcome in a fetus with an extremely low heart rate due to isolated complete congenital heart block.

Isolated complete congenital heart block (CCHB) in a fetus is usually associated with the presence of autoantibodies to SSA (Ro) and SSB (La) antigens in the maternal circulation. Although the prognosis for the majority of fetuses is good, it is less favorable in fetuses with a ventricular rate < 55 bpm in early pregnancy or with a decrease in the ventricular rate by >/= 5 bpm during pregnancy. It is not known if the same prognostic criteria apply for the occasional fetus with isolated non-autoimmune CCHB. We report a case of a single fetus with an isolated non-autoimmune CCHB with an extremely low ventricular rate (37 bpm) in which the outcome was favorable. Dilated cardiomyopathy is a rare complication in patients with isolated CCHB, despite early institution of cardiac pacing, and is usually recognized after several months of relative well-being. It is assumed that in the majority of patients it represents a sequel to in utero autoimmune or postnatal reactivation myocarditis. However, the possibility of a tachycardia-induced cardiomyopathy caused by an excessively high pacing rate should also be taken into consideration, as was clearly demonstrated in our patient.

Simulation of cardiovascular physiology: the diastolic function(s) of the heart.

The cardiovascular system was simulated by using an equivalent electronic circuit. Four sets of simulations were performed. The basic variables investigated were cardiac output and stroke volume. They were studied as functions (i) of right ventricular capacitance and negative intrathoracic pressure; (ii) of left ventricular relaxation and of heart rate; and (iii) of left ventricle failure. It seems that a satisfactory simulation of systolic and diastolic functions of the heart is possible. Presented simulations improve our understanding of the role of the capacitance of both ventricles and of the diastolic relaxation in cardiovascular physiology.

Morphological variations of secundum-type atrial septal defects: feasibility for percutaneous closure using Amplatzer septal occluders.

The aim of the study was to assess the morphology of secundum-type atrial septal defects (ASD) with a view to percutaneous closure using Amplatzer septal occluders (ASO). One hundred and ninety patients who underwent closure of isolated secundum-type ASD between September 1995 and January 2000 were included. The morphology of the defects was studied using transthoracic and transesophageal echocardiography. Patients with defects of suitable morphology and size underwent percutaneous closure using ASO. The remaining patients underwent surgical closure. Centrally placed defects were observed in 46 patients (24.2%). Morphological variations of secundum-type ASD were detected in 144 patients (75.8%). One hundred and fifty-one patients (79.5%) underwent percutaneous closure using ASO. Thirty-nine patients (20.5%) underwent surgical closure. Centrally placed defects, defects with deficient superior anterior rim, multiple defects, and perforated aneurysms of the interatrial septum are morphological variations of secundum-type ASD suitable for percutaneous closure using ASO. Cathet Cardiovasc Intervent 2001;53:386-391.

Percutaneous closure of patent ductus arteriosus: complementary use of detachable Cook patent ductus arteriosus coils and Amplatzer duct occluders.

UNLABELLED: Several different devices were evaluated for the percutaneous closure of patent ductus arteriosus (PDA), and important drawbacks were found in all of them. To overcome these drawbacks, both detachable Cook PDA coils and Amplatzer duct occluders (ADO) were used for the percutaneous closure of PDA. A total of 54 patients underwent transcatheter occlusion of PDA at a median age of 4.5 years (range 0.5-29 years) and at a median weight of 19.5 kg (range 6-69 kg). Three patients were adults. Detachable Cook PDA coils were used in 26 patients with a median PDA diameter of 1.7 mm (range 1.1-2.2 mm) and ADO were used in 28 patients with a median PDA diameter of 3.8 mm (range 1.9-7.5 mm). Devices were successfully implanted in all 54 patients. Complete closure was achieved in 53 of 54 patients (98% closure rate). Median fluoroscopy time was 12 min (range 4-47 min). CONCLUSION: According to our experience, the complementary use of detachable Cook patent ductus arteriosus coils and Amplatzer duct occluders for the percutaneous closure of PDA can be recommended.

Transcatheter occlusion of residual patent ductus arteriosus after surgical ligation.

The reported frequency of residual leaks after surgical ligation of patent ductus arteriosus (PDA) varies from 6% to 23%. Reports on percutaneous closure of PDA also involve patients with residual PDA after ligation, but specific data regarding this type of PDA are rare. Our objective was to assess retrospectively the characteristics of residual PDA relevant to transcatheter closure and occlusion results using three types of occluders. Twelve consecutive patients underwent transcatheter occlusion of residual PDA after surgical ligation at a median age of 4.6 years (range 3. 2-44.6 years) and median weight 16.5 kg (range 13-62 kg). Three types of occluder were used: Gianturco coils, detachable Cook PDA coils, and the new Amplatzer duct occluder. The median diameter of residual PDA after ligation was 1.5 mm (range 0.9-4.2 mm). All PDAs were of type A morphology. Thirteen devices were successfully placed in the 12 patients, without embolization. There were no complications. At 1 month and 1 year follow-up all residual shunts were completely closed. Coils are particularly suitable for complete closure of residual leaks after surgical ligation of PDA. A 100% closure rate was achieved with a low number of implanted coils.

Percutaneous closure of patent ductus arteriosus using special screwing detachable coils.

Jackson screwing detachable coils, developed for arterial and venous embolization, have been successfully employed recently for the percutaneous occlusion of patent ductus arteriosus (PDA). Special screwing detachable coils were designed for closure of the PDA, and the experience gained by their use is described in this report. Occlusion was attempted in 29 patients with a minimal ductal diameter of 0.9-4.2 mm. Coils were successfully placed in all 29 patients. One coil, which embolized 10 min after detachment, was retrieved. In 26 patients (89%), complete closure was achieved. Only 35 coils were placed in 29 patients. Residual shunts in three patients are minimal, detectable only on color-flow mapping. Screwing detachable coils for closure of PDA are safe and effective for occlusion of PDA with a minimal diameter < 4.2 mm. Embolization of the coil is very rare. A high closure rate is achieved with a low number of placed coils.