Beta-blockade at low doses restoring the physiological balance in myocytic antagonism

Objective: The ventricular mass is organized in the form of meshwork, with populations of myocytes aggregated in a supporting matrix of fibrous tissue, with some myocytes aligned obliquely across the wall so as to work in an antagonistic fashion compared to the majority of myocytes, which are aggregated together in tangential alignment. Prompted by results from animal experiments, which showed a disparate response of the two populations of aggregated myocytes to negative inotropic medication, we sought to establish whether those myocytes that aggregated so as to extend obliquely across the thickness of the ventricular walls are more sensitive to beta-blockade than the prevailing population in which the myocytes are aggregated together with tangential alignment. If the two populations respond in similar differing fashion in the clinical situation, we hypothesize that this might help to explain why drugs blocking the beta-receptors improve function of the ventricular pump in the setting of congestive cardiac failure. Methods: We implanted needle probes in 13 patients studied during open heart surgery, measuring the forces generated in the ventricular wall and seeking to couple the probes either to myocytes aggregated together with tangential alignment or to those aggregated in oblique fashion across the ventricular walls. In a first series of patients, we injected probatory doses intravenously, amounting to a total bolus of 40-100mg Esmolol, while in a second series, we gave fixed yet rising doses of 5, 10, and 20mg Esmolol in three separate boluses. Results: Forces recorded in the aggregated myocytes with tangential alignment decreased insignificantly upon administration of low doses (57.1±12.4mN→56.6±7.6mN), while forces recorded in the myocytes aggregated obliquely across the ventricular wall showed a significant decrease in the mean (59.3±11.6mN→47.4±6.4mN). Conclusions: The markedly disparate action of drugs blocking beta-receptors at low dosage seems to be related to the heterogeneous extent, and time course, of systolic loading of the myocytes. This, in turn, depends on whether the myocytes themselves are aggregated together with tangential or oblique alignments relative to the thickness of the ventricular wall

Cardiac surgery for Chagas disease

Although Chagas disease is a rare entity in North America, it is associated with significant cardiac morbidity. It is estimated that 20‐30% of those who are infected will eventually develop cardiovascular disease secondary to Chagas disease. We review the literature and share our experience on the surgical management of this challenging patient population

Beta-blockade at low doses restoring the physiological balance in myocytic antagonism

Objective: The ventricular mass is organized in the form of meshwork, with populations of myocytes aggregated in a supporting matrix of fibrous tissue, with some myocytes aligned obliquely across the wall so as to work in an antagonistic fashion compared to the majority of myocytes, which are aggregated together in tangential alignment. Prompted by results from animal experiments, which showed a disparate response of the two populations of aggregated myocytes to negative inotropic medication, we sought to establish whether those myocytes that aggregated so as to extend obliquely across the thickness of the ventricular walls are more sensitive to beta-blockade than the prevailing population in which the myocytes are aggregated together with tangential alignment. If the two populations respond in similar differing fashion in the clinical situation, we hypothesize that this might help to explain why drugs blocking the beta-receptors improve function of the ventricular pump in the setting of congestive cardiac failure. Methods: We implanted needle probes in 13 patients studied during open heart surgery, measuring the forces generated in the ventricular wall and seeking to couple the probes either to myocytes aggregated together with tangential alignment or to those aggregated in oblique fashion across the ventricular walls. In a first series of patients, we injected probatory doses intravenously, amounting to a total bolus of 40-100mg Esmolol, while in a second series, we gave fixed yet rising doses of 5, 10, and 20mg Esmolol in three separate boluses. Results: Forces recorded in the aggregated myocytes with tangential alignment decreased insignificantly upon administration of low doses (57.1±12.4mN→56.6±7.6mN), while forces recorded in the myocytes aggregated obliquely across the ventricular wall showed a significant decrease in the mean (59.3±11.6mN→47.4±6.4mN). Conclusions: The markedly disparate action of drugs blocking beta-receptors at low dosage seems to be related to the heterogeneous extent, and time course, of systolic loading of the myocytes. This, in turn, depends on whether the myocytes themselves are aggregated together with tangential or oblique alignments relative to the thickness of the ventricular wall

Partial Left Ventriculectomy to Treat End-Stage Heart Disease

Background. It is reasoned that reducing left ventricular diameter (Laplace’s law) in patients with dilated cardiomyopathy, will improve ventricular function. Methods. Partial left ventriculectomy was performed in 120 patients with end-stage dilated cardiomyopathies of varying causes. Most patients were in New York Heart Association functional class IV. The procedure consisted of removal of a wedge of left ventricular muscle from the apex to the base of the heart. Depending on the distance between the two papillary muscles, the mitral valve apparatus was either preserved, repaired, or replaced with a tissue prosthesis. Results. The 30-day mortality was 22% and the 2-year survival was 55%. Although 10% of surviving patients showed no improvement in New York Heart Association functional class, most of the surviving patients were in either class I (57%) or II (33.3%), and the others were in class III and IV. Conclusions. Partial left ventriculectomy can be used to treat end-stage dilated cardiomyopathy. Further studies and a longer follow-up period are needed to fully assess the effects of this procedure

Autotransplante cardíaco: um novo método no tratamento de problemas cardíacos complexos Heart autotransplantation: a new technique to complex intracardiac reppairs

No período de janeiro de 1990 a maio de 1995 foram operados com a técnica do autotransplante cardíaco 92 pacientes com cardiopatias complexas e arritmias supraventriculares, principalmente fibrilação atrial (n=89), reentrada (n=2), QT longo (n=1). O sexo feminino predominou (n=63). A idade variou de 18 a 76 anos (m=43). Os defeitos concomitantes foram: átrio esquerdo gigante (medido pelo ecocardiograma > 6 cm) (n=65); átrio direito gigante (n=9); átrio esquerdo aumentado (4 cm) (n=23); estenose mitral (n=46); insuficiência mitral (n=28); dupla lesão mitral (n=16); estenose aórtica (n=12); insuficiência aórtica (n=5); insuficiência tricúspide (n=78); trombose atrial (n=23); calcificação atrial (n=12); hipertensão pulmonar (n=86); fibroelastose biventricular (n=3); rotura atrioventricular (pós-troca de valva mitral) (n=1); aneurisma da raiz aórtica (n=1); ventriculectomia parcial (n=8); 88 pacientes saíram do centro cirúrgico em ritmo sinusal e assim permaneceram; 6 precisaram de drogas inotrópicas e 3 de drogas antiarrítmicas. Todos os pacientes que apresentavam átrio esquerdo ou direito gigante com fibrilação atrial tiveram seus átrios reduzidos ao tamanho normal. Não houve mortalidade operatória e 6 evoluíram a óbito hospitalar. Na reavaliação aos seis meses de pós-operatório, os sobreviventes estavam bem, em ritmo sinusal. A técnica do autotransplante cardíaco facilita o reparo intracardíaco, proporciona a redução atrial e conseqüente retorno do paciente ao ritmo sinusal e abre novas perspectivas.From January 1990 to May 1995,92 patients with complex cardiac problems and supraventricular arrhythmias were operated upon with the technique of heart autotransplantation. The arrhythmias were: atrial fibrillation (n=89); reentry (n=2); long QT syndrome (n=1). Females predominated (n=63). The age varied from 18 to 76 years (m=43). Concomittant defects were: giant left atrium (> 6 cm measured by echo) (n=65); giant right atrium (n=9); large left atrium (4 cm) (n=23); mitral stenosis (n=46); mitral insufficiency (n=28); mitral double lesion (n=16); aortic stenosis (n=12); aortic insufficiency (n=5); tricuspid insufficiency (n=75); atrial thrombosis (n=23); atrial calcification (n=12); pulmonnary hypertension (n=86); biventricular fibroelastose (n=3); atrioventricular rupture (n=1); aortic root aneurysm (n=1); partial ventriculectomy (n=8); 88 patients left the operating room and remained in sinus rhythm; 6 required inotropic drugs and 3 antiarrhythmic drugs. All patients with giant atria and atrial fibrillation had their atria reduced to normal sizes. There were no OR mortality and 6 patients died during hospitalization. Six months later the survivors were clinically well, in sinus rhythm. The technique of heart autotransplantation facilitates intracardiac reppairs, provides atrial reduction and returns patients with atrial fibrillation into sinus rhythm, and opens new frontiers