Bioeffects of albumin-encapsulated microbubbles and real-time myocardial contrast echocardiography in an experimental canine model

Myocardial contrast echocardiography has been used for assessing myocardial perfusion. Some concerns regarding its safety still remain, mainly regarding the induction of microvascular alterations. We sought to determine the bioeffects of microbubbles and real-time myocardial contrast echocardiography (RTMCE) in a closed-chest canine model. Eighteen mongrel dogs were randomly assigned to two groups. Nine were submitted to continuous intravenous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) plus continuous imaging using power pulse inversion RTMCE for 180 min, associated with manually deflagrated high-mechanical index impulses. The control group consisted of 3 dogs submitted to continuous imaging using RTMCE without PESDA, 3 dogs received PESDA alone, and 3 dogs were sham-operated. Hemodynamics and cardiac rhythm were monitored continuously. Histological analysis was performed on cardiac and pulmonary tissues. No hemodynamic changes or cardiac arrhythmias were observed in any group. Normal left ventricular ejection fraction and myocardial perfusion were maintained throughout the protocol. Frequency of mild and focal microhemorrhage areas in myocardial and pulmonary tissue was similar in PESDA plus RTMCE and control groups. The percentages of positive microscopical fields in the myocardium were 0.4 and 0.7 percent (P = NS) in the PESDA plus RTMCE and control groups, respectively, and in the lungs they were 2.1 and 1.1 percent, respectively (P = NS). In this canine model, myocardial perfusion imaging obtained with PESDA and RTMCE was safe, with no alteration in cardiac rhythm or left ventricular function. Mild and focal myocardial and pulmonary microhemorrhages were observed in both groups, and may be attributed to surgical tissue manipulation.

Efeitos eletrocardiográficos e hemodinâmicos do cloridrato de amiodarona por via venosa / Electrocardiographic and hemodynamic effects of amiodarone hydrochloride by intravenous route

Quatorze pacientes portadores de cardiomiopatia chagasica cronica, com arritmias ventriculares persistentes e insuficiencia miocardica, foram submetidos a avaliacao eletrocardiografica continua por periodo de 24 horas (em 12 pacientes) e a estudo hemodinamico, antes (condicao de controle) e apos (condicao 20, 40 e 60 minutos) a administracao de 5 mg/kg de peso seguida por infusao venosa continua de 900 a 1050 mg de cloridrato de amiodarona (AM) por periodo de 24 horas. Houve reducao porcentual media de 73,5% no numero de extra-sistoles ventriculares sem modificacoes apreciaveis nos episodios de taquicardia ventricular. Entre as condicoes 20 e 60 minutos, ocorreu diminuicao significativa da frequencia cardiaca (FC) e do indice cardiacao e aumento nas pressoes media do atrio direito (AD), na diastolica final do ventriculo esquerdo e nas resistencias arterial pulmonar e vascular sistemica. Com excecao dos valores da FC e da AD, as demais variaveis hemodinamicas retornaram aos valores de controle 24 horas a infusao venosa continua de AM. Em vista da depressao da funcao cardiaca que persistiu ate 60 minutos, concluiu-se que o AM deve ser cuidadosamente administrado principalmente em pacientes con insuficiencia miocardica