Search

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.

Heart transplantation is a good option for heart failure, but there are not many organ donors; even in the most developed countries of the world, only 1% of those who need heart transplantation will receive it. The situation is even worse in Brazil. So I would like to discuss a procedure I developed for the 99% of patients who do not have access to heart transplantation, which is the partial left ventriculectomy (PLV). Its concept is that rather than operating on the heart, I am operating on its diameter. If you look at the heart as a bad muscle, it does not make any sense to excise a piece of it in order to make it better because the heart needs more muscle. Why then does the patient improve? It has to do with the diameter. Nature has been shaping the heart for 100 million years, which is a great deal of experience bringing it to where it is today. The snake heart is very tiny, and if it is placed beside a human heart and a buffalo heart, it is immediately recognized as a snake heart (Fig. 1). But if a computer image of the snake heart is enlarged to the size of the buffalo heart, you can no longer determine which is which. The ratio of mass to diameter is the same in both hearts. In fact, all hearts have the same ratio of mass to diameter, from the snake to the buffalo to the whale. Everything in nature, from strawberries to oranges to hearts, has the same ratio, regardless of its size. Thus there is a single formula common to all hearts in nature, which is that muscle mass is four times the radius cubed (M = 4 × R). A small snake heart is 1 cm and 5 g (Fig. 2). A human heart is five times larger and has 100 times more muscle mass; an ox heart is ten times larger and has 1000 times more muscle mass. Any heart that is not within this formula simply needs to be returned to it. Fig. 3 shows a transplanted heart that looks like a normal ox heart from the outside, but cross-sections reveal that it is not (Fig. 4). For this heart to be normal, either the cavity must be filled with muscle or the diameter must be decreased. Fig. 5 shows what the heart looks like if its diameter is decreased. Removing a piece of the heart and decreasing its diameter returns it to its natural state, where the diameter is appropriate for the amount of muscle. We performed experiments in sheep to determine the importance of the heart’s diameter. In a normal heart we split the ventricle in two and added a patch to increase the diameter of the heart (Fig. 6). What happened? The heart simply stopped and would no longer beat. To cause it to beat again, we excised the patch. So if I were to increase the diameter of a heart by 20%, heart function (ejection fraction) would decrease by 30%. If I were to decrease the heart by 1 cm, the effect would be the same as if I added 1 kg of muscle. That is the importance of the diameter. Fig. 7 is magnetic resonance imaging showing how thick the muscle is in one area and how thin in another. If we bring one edge to the other, decreasing the diameter of the heart, it will beat much better. A dilated heart contracts isometrically, that is, it expends a lot of energy without doing much work. If I reduce it to a size that I can hold in only one hand, the resulting curvature will strengthen the heart’s ability to contract. Two groups from Japan and the Netherlands measured pressure/volume loops both before and after PLV in approximately 120 of my patients by putting pressure and conductance catheters through the apex of the heart or the European Journal of Cardio-thoracic Surgery 15 (Suppl. 1) (1999) S12–S19

Background: Attempts to prolong life or to improve the quality of life by partial left ventriculectomy in patients suffering from dilated cardiomyopathy have yielded strikingly variable results in leading surgical centers. Hypothesis: The outcome of patients after partiat left ventriculectomy depends on intraoperative myocardial protection together with appropriate long-term pharmacotherapy. We further assume that partial removal of the fibrotic ventricular wall may lead to a particularly inhomogeneous pattern of wall stress, giving rise to the potential of a paradoxical increase in wall stress and the creation of arrhythmogenic foci. Methods: During surgery in 24 patients, local mesh tension was measured using needle-force probes in up to five sites within the left ventricular wall before and after resection of the interpapillary mural segment. The data were used to calculate regional peak developed force and to identify any differences in the timing of local mechanical activity between the measured regions. Results: Mean decrease in regional wall stress was 42% (76 sites of measurement). However, we discovered a paradoxicat increase of 42% in 18 sites of measurement. The time delay in the onset of force development between the measured regions prior to surgery was 0 msec in 10 patients, up to 30 msec in 7 patients, and beyond 80 msec in 7 patients. After resection, the time delay increased considerably in incidence and duration. Conclusion: Ventriculectomy is an effective means of reducing wall stress. The unexpectedly high incidence of inhomogeneities in wall stress after asymmetrical surgical ventricular remodeling, currently typical for the classical Batista procedure, together with the asynchronous regional ventricular function that we found to increase after partial left ventriculectomy, needs further elucidation by electrophysiological investigations.

A melhora clínica da função cardíaca pós aneurismectomia de ventrículo esquerdo e/ou cardiomioplastia com o músculo grande dorsal parece ser, ao menos parcialmente, devida ao remodelamento do ventrículo esquerdo. Através de pesquisa em nosso laboratório experimental com carneiros, demonstramos que o aumento do diâmetro do ventrículo é mais importante que a perda de massa muscular para a deterioração da função ventricular. Sabendo-se que em miocardiopatia dilatada não ocorre aumento de massa muscular, reduzimos o diâmetro do ventrículo para o normal, em uma série consecutiva de pacientes com esta lesão. No período de 1984 a 1995, foram operados com esta nova técnica, denominada, então, "Ventriculectomia Parcial", 103 pacientes portadores de miocardiopatias complexas e insuficiência cardíaca congestiva (NYHA IV). A operação é baseada na lei de Laplace (T=P.11.D) e consistiu na remoção de uma fatia de músculo da parede lateral do ventrículo esquerdo, iniciando-se na ponta deste, estendendo-se entre os músculos papilares e terminando próximo ao anel mitral. A cirurgia é realizada sob circulação extracorpórea normotérmica e não se utiliza cardioplegia. "Todos os pacientes foram avaliados pré-operatoriamente com ecodopplercardiografia e ventriculografia digital, os quais revelaram fração de ejeção < 20%, confirmando estes pacientes como candidatos ao transplante cardíaco. A maioria era do sexo masculino (n=73) e a idade variou de 19 a 74 anos. As doenças foram: miocardite a virus (n=12); pós miocardioplastia (n=1); doença de Chagas (n=15); doença valvar (n=38); doença isquémica (n=16); idiopática (n=21). Óbitos hospitalares (ocorridos nos primeiros 30 dias da cirurgia) (n=13): embolia pulmonar (n=4); insuficiência renal (n=5); sangramento (n=4). Óbitos tardios (ocorridos depois do 30º dia de cirurgia) (n=10): arritmia (n=6); "insuficiência cardíaca" (n=2); causa desconhecida (n=2); 8 pacientes precisaram ser reoperados por sangramento. Não houve infecção e nenhum paciente precisou balão intra-aórtico. Todos saíram com nitroprussiato e 19 pacientes, com inotrópicos. A ventriculografia e a ecocardiografia pós-op mostraram melhora acentuada da FE (de 100% a 300%). Em conclusão, a nova técnrca "Ventriculectomia Parcial", com o objetivo de reduzir o diâmetro do ventrículo esquerdo, pode beneficiar pacientes em estágio final de cardiopatia dilatada. Este novo conceito pode, na nossa experiência, proporcionar ao paciente melhora clínica significativa e prolongamento de sua vida.The clinical improvement of cardiac function post left ventricular aneurysmectomy and/or cardiomyoplasty with the latissimus dorsi muscle seems to be due to the remodeling of the left ventricle. We did some experiments with sheep in our laboratory and we concluded that the increment of ventricular diameter is more deleterious than loss of muscle mass to the ventricular function. Since there is no increment in muscle mass to the dilated hearts, we reduced their diameter to accomplish a better ventricular function in a series of very sick patients with dilated hearts. From 1984 to 1995, 103 patients with complex cardiac problems and end stage congestive heart failure (NYHA IV) with dilated cardiomyopathy underwent "Partial Ventriculectomy". The operation was based on Laplace's law (T-P.II.D) and consisted of removal of a large wedge of muscle from the lateral wall of the left ventricle beginning at the apex and extending between the papillary muscles, ending proximal to the mitral annulus. The operation was performed under normothermic cardiopulmonary bypass and no cardioplegia was used. Pre-operative left ventriculography and echocardiography showed global hypocontractility of the hearts with ejection fraction lower than 20% in all patients who were considered candidates for cardiac transplantation. Males were predominant (n=73) and the age varied from 19 to 74 years. The pathologies were: viral miocarditis (n=12); post miocardioplasty (n=1); Chagas' disease (n=15); valvular disease (n=38); ischemic disease (n=16); idiopathic (n=21). Hospital mortality (30 days post operative) (n=13): pulmonary embolus (n=4); renal failure (n=5); bleeding (n=4). Late deaths (after 30 days post-operative) (n=10): arhythmia (n=6); "cardiac failure" (n=2); unknown (n=2); 8 patients required reoperation for bleeding. There were no infection and none required IAPB. All patients had nipride and 19 needed inotropics. Post-op ventriculographies and echocardiographies showed improvement of EF (from 100% to 300%). In conclusion, this new technique "Partial Ventriculectomy", with it's purpose of reducing the ventricular diameter, may benefit patients with end stage heart failure. And this new concept may, in our experience, give the patient improvement in his clinical status and increase life span.

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 (< 6 cm/>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 (< 6 cm./>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.

Entre 1982 e 1988 24 mulheres e 6 homens com miastenia gravis foram submetidos a protocolo diagnóstico e terapêutico prospectivo e estandardizado. A idade variou de 10 a 74 anos (34±16, média±desvio padrão). Três com forma ocular foram tratados com piridostigmina. Quatro com forma generalizada, de idade avançada, receberam corticosteróide e/ou azatioprina. Vinte e três com a forma generalizada foram submetidos a timectomia seguida de prednisona e/ou azatioprina. Um paciente faleceu após timectomia complexa de timoma invasivo. Qutro faleceu logo após a admissão, em crise miastênica/colinérgica. Dois outros tiveram complicações menores da timectomia. De 19 pacientes seguidos por 1-60 (média 24) meses, 11 (58%) têm fraqueza residual mas levam vida normal e 8 (42%) estão em remissão completa, um sem medicação. Between 1982 and 1988 24 women and 6 men with myasthenia gravis were included in a prospective and standardized diagnostic and therapeutic protocol. Age varied between 10 and 74 years (34 ± 16, mean ± standard deviation). Three patients with the ocular form were treated with pyridostigmine. Four patients with the generalized form and advanced age received steroids and/or azathioprine. Twenty-three patients with the generalized form underwent thymectomy followed by prednisone and/or azathioprine. One patient died after complex thymectomy for invasive thymoma. Another died soon after admission in myasthenic/cholinergic crisis. Two other patients had minor complications of thymectomy. Of 19 patients followed for 1-60 (mean 24) months, 11 (58%) are in remission, one of them without any medication.

At its introduction, partial left ventriculectomy was seen as a promising option. 1 As initially used, its main drawback was its unpredictable effect on cardiac function. The size, shape, and location of the segment to be resected were at the discretion of the surgeon. Once the segment had been resected, any disadvantageous results were irreversible. Resection, and subsequent coaptation of the incision, often compromised coronary perfusion. 2 Experience showed that insufficient narrowing of the ventricular base could cause late postoperative mitral valvular incompetence. 3 Right ventricular function was also impaired by extensive resections from the left ventricle. 4 A further reported complication is sudden death from ventricular fibrillation, which reportedly occurred within 6 months of the intervention. 5 Encouraging initial clinical results 1,6-8 nonetheless have shown that the basic concept of partial left ventriculectomy is sound, at least when conceived as a bridging procedure. To validate the technique and improve its results, we have devised an off-pump strategy that permits reduction of ventricular radius by plication of a chosen segment of ventricular wall. By using aspirator cups, we avoid an open procedure. The technique permits initial sequestration in trial fashion, allowing us to assess ventricular function. Only if it is judged satisfactory do we then perform the definitive ventricular plication. Our new technique of sutured splinting for the definitive plication preserves the coronary vasculature.

Surgical strategies recently introduced to improve ventricular function have been based on the concepts of reduction of ventricular diameter, synchronization of myocardial activity, passive support of diastolic ventricular shape, and active support of systolic ventricular constriction. They have depended on several established theoretical assumptions, not all of which are totally valid. Clinical results have proved markedly variable. This is especially true for procedures designed to reduce the radius of the left ventricle. Some have reported up to 80% mortality, whereas others achieve results comparable with those for heart transplantation. Because of this, the method runs the risk to be rejected, or else, its more widespread application will be postponed until essential details concerning the basic concepts have been elucidated. It is these details which we discuss in this review.

Nine months after partial ventriculectomy, a 53-year-old man died of progressive heart failure. His heart was examined to determine the alignment of the muscle fibers around the ventricular scar, which was 11 cm long, 1.3 cm thick and 4 cm wide. The scar reached 2 to 12 mm beyond the surgical suture line. The fibers in the middle and subendocardial layers were malaligned, resulting in convergence, compression and regional necrosis.

Background —Partial left ventriculectomy (PLV) is a novel surgical treatment for severe heart failure consisting of resection of a large wedge of myocardium to reduce wall stress and restore the normal mass-volume ratio. Although ejection fraction (EF) has been shown to improve after PLV, few other physiological data describing its immediate effects on left ventricular (LV) performance are available. Methods and Results —Eight patients, 58±5 years old, with severe clinical heart failure and EF of 12±3% were studied before and immediately after PLV. LV performance was assessed by the predominantly load-insensitive measures of pressure-area relations with high-fidelity pressure catheters and transesophageal automated echocardiographic measures of cross-sectional area as a surrogate for volume. LV end-diastolic volume decreased from 200±60 to 89±17 mL, EF increased from 12±3% to 41±8%, and right ventricular (RV) fractional area change increased from 24±12% to 37±16% (all P 2 and preload recruitable stroke work, 33±16 to 34±19 mm Hg ( P =NS versus before). End-diastolic stiffness increased from 0.13±0.06 to 0.19±0.07 mm Hg/cm 2 ( P Conclusions —PLV resulted in reductions in LV volumes, increases in EF and RV ejection, but increases in LV stiffness. Estimates of LV performance revealed variable results associated with the degree of myocardial fibrosis. Further study of these effects in relation to patient outcome is warranted.

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.

A melhora clínica da função cardíaca pós aneurismectomia de ventrículo esquerdo e/ou cardiomioplastia com o músculo grande dorsal parece ser, ao menos parcialmente, devida ao remodelamento do ventrículo esquerdo. Através de pesquisa em nosso laboratório experimental com carneiros, demonstramos que o aumento do diâmetro do ventrículo é mais importante que a perda de massa muscular para a deterioração da função ventricular. Sabendo-se que em miocardiopatia dilatada não ocorre aumento de massa muscular, reduzimos o diâmetro do ventrículo para o normal, em uma série consecutiva de pacientes com esta lesão. No período de 1984 a 1995, foram operados com esta nova técnica, denominada, então, "Ventriculectomia Parcial", 103 pacientes portadores de miocardiopatias complexas e insuficiência cardíaca congestiva (NYHA IV). A operação é baseada na lei de Laplace (T=P.11.D) e consistiu na remoção de uma fatia de músculo da parede lateral do ventrículo esquerdo, iniciando-se na ponta deste, estendendo-se entre os músculos papilares e terminando próximo ao anel mitral. A cirurgia é realizada sob circulação extracorpórea normotérmica e não se utiliza cardioplegia. "Todos os pacientes foram avaliados pré-operatoriamente com ecodopplercardiografia e ventriculografia digital, os quais revelaram fração de ejeção < 20%, confirmando estes pacientes como candidatos ao transplante cardíaco. A maioria era do sexo masculino (n=73) e a idade variou de 19 a 74 anos. As doenças foram: miocardite a virus (n=12); pós miocardioplastia (n=1); doença de Chagas (n=15); doença valvar (n=38); doença isquémica (n=16); idiopática (n=21). Óbitos hospitalares (ocorridos nos primeiros 30 dias da cirurgia) (n=13): embolia pulmonar (n=4); insuficiência renal (n=5); sangramento (n=4). Óbitos tardios (ocorridos depois do 30º dia de cirurgia) (n=10): arritmia (n=6); "insuficiência cardíaca" (n=2); causa desconhecida (n=2); 8 pacientes precisaram ser reoperados por sangramento. Não houve infecção e nenhum paciente precisou balão intra-aórtico. Todos saíram com nitroprussiato e 19 pacientes, com inotrópicos. A ventriculografia e a ecocardiografia pós-op mostraram melhora acentuada da FE (de 100% a 300%). Em conclusão, a nova técnrca "Ventriculectomia Parcial", com o objetivo de reduzir o diâmetro do ventrículo esquerdo, pode beneficiar pacientes em estágio final de cardiopatia dilatada. Este novo conceito pode, na nossa experiência, proporcionar ao paciente melhora clínica significativa e prolongamento de sua vida. The clinical improvement of cardiac function post left ventricular aneurysmectomy and/or cardiomyoplasty with the latissimus dorsi muscle seems to be due to the remodeling of the left ventricle. We did some experiments with sheep in our laboratory and we concluded that the increment of ventricular diameter is more deleterious than loss of muscle mass to the ventricular function. Since there is no increment in muscle mass to the dilated hearts, we reduced their diameter to accomplish a better ventricular function in a series of very sick patients with dilated hearts. From 1984 to 1995, 103 patients with complex cardiac problems and end stage congestive heart failure (NYHA IV) with dilated cardiomyopathy underwent "Partial Ventriculectomy". The operation was based on Laplace's law (T-P.II.D) and consisted of removal of a large wedge of muscle from the lateral wall of the left ventricle beginning at the apex and extending between the papillary muscles, ending proximal to the mitral annulus. The operation was performed under normothermic cardiopulmonary bypass and no cardioplegia was used. Pre-operative left ventriculography and echocardiography showed global hypocontractility of the hearts with ejection fraction lower than 20% in all patients who were considered candidates for cardiac transplantation. Males were predominant (n=73) and the age varied from 19 to 74 years. The pathologies were: viral miocarditis (n=12); post miocardioplasty (n=1); Chagas' disease (n=15); valvular disease (n=38); ischemic disease (n=16); idiopathic (n=21). Hospital mortality (30 days post operative) (n=13): pulmonary embolus (n=4); renal failure (n=5); bleeding (n=4). Late deaths (after 30 days post-operative) (n=10): arhythmia (n=6); "cardiac failure" (n=2); unknown (n=2); 8 patients required reoperation for bleeding. There were no infection and none required IAPB. All patients had nipride and 19 needed inotropics. Post-op ventriculographies and echocardiographies showed improvement of EF (from 100% to 300%). In conclusion, this new technique "Partial Ventriculectomy", with it's purpose of reducing the ventricular diameter, may benefit patients with end stage heart failure. And this new concept may, in our experience, give the patient improvement in his clinical status and increase life span.

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 (< 6 cm/>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.

A stentless pericardial aortic monopatch was used in 60 consecutive patients undergoing aortic valve replacement The monopatch is constructed of a sheet of glutaraldehyde-treated bovine pericardium, tailored and shaped to fit the aortic anulus, and is sutured in place without a stent or sewing ring. The valve area is effectively preserved by this method. Results indicate that this technique is simple, inexpensive, and applicable to all cases of aortic valve disease. It does not require anticoagulation and may allow for annular growth when used in children. This technique is particularly suitable for patients with infective endocarditis because the amount of foreign material is minimized.

Recent morphological studies provide evidence that the ventricular walls are arranged as a 3D meshwork of aggregated cardiomyocyte chains, exhibiting marked local structural variations. In contrary to previous findings, up to two-fifths of the chains are found to have a partially transmural alignment, thus deviating from the prevailing tangential orientation. Upon contraction, they produce, in addition to a tangential force, a radial force component that counteracts ventricular constriction and aids widening of the ventricular cavity. In experimental studies, we have provided evidence for the existence of such forces, which are auxotonic in nature. This is in contrast to the tangentially aligned myocytes that produce constrictive forces, which are unloading in nature. The ventricular myocardium is, therefore, able to function in an antagonistic fashion, with the prevailing constrictive forces acting simultaneously with a dilatory force component. The ratio of constrictive to dilating force varies locally according to the specific mural architecture. Such antagonism acts according to local demands to preserve the ventricular shape, store the elastic energy that drives the fast late systolic dilation and apportion mural motion to facilitate the spiralling nature of intracavitary flow. Intracavitary pressure and flow dynamics are thus governed concurrently by ventricular constrictive and dilative force components. Antagonistic activity, however, increases deleteriously in states of cardiac disease, such as hypertrophy and fibrosis. β-blockade at low dosage acts selectively to temper the auxotonic forces.