Dobutamine myocardial scintigraphy for the prediction of cardiac events after heart transplantation.

BACKGROUND: The long-term outcome after heart transplantation (HTx) is essentially influenced by the occurrence and extent of cardiac allograft vasculopathy (CAV). Single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has been shown to be a useful and cost-effective non-invasive method in patients with known or suspected coronary artery disease, but its role in detecting CAV remains unclear. AIM: To evaluate the accuracy and predictive value of dobutamine MPI in patients after HTx during a 12-month follow-up. METHODS: Seventy-seven patients (60 males, 17 females) underwent a total of 216 dobutamine MPI examinations over a period of 5 years. Examinations were obtained an average of 89+/-42 months after orthotopic HTx according to a 1-day protocol using 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) with and without attenuation correction. For the present study, findings from 77 MPI examinations (one MPI examination per patient) were analysed visually and semiquantitatively using a 20-segment model. Summed stress scores (SSS) and summed rest scores (SRS) were calculated and receiver operating characteristic (ROC) analysis was performed to detect optimum threshold values. Patients were followed up for 12 months and cardiac events were registered. RESULTS: Cardiac events were observed in 10 of the 77 patients. Good interobserver agreement was found for global visual and SRS-/SSS-based analysis (kappa=0.74 and 0.66, respectively). SSS was superior to SRS in the detection of cardiac events. ROC analysis showed an optimized SSS threshold value of three. For predicting a cardiac event during the 12-month follow-up, global visual and semiquantitative analysis reached sensitivities of 90% and 90%, specificities of 72% and 88%, accuracies of 74% and 87%, positive predictive values of 32% and 53% and negative predictive values of 98% and 98%, respectively. The sensitivity, specificity, accuracy and positive and negative predictive values for MPI to detect clinically relevant coronary artery stenoses (> or =50%) at conventional coronary angiography were 83%, 87%, 86%, 56% and 96%, respectively. CONCLUSIONS: Non-invasive dobutamine MPI reliably identifies patients at risk for subsequent cardiac events in cases of CAV, with a high negative predictive value of 98% and an accuracy of 87%.

Relaçäo entre tempo de isquemia e performance pós-operatória no transplante cardíaco / Relationship between ischemic time and postoperative performance in heart transplantation

A presente dificuldade na obtençao de doadores adequados para o transplante cardíaco obriga à necessidade da utilizaçao de órgaos removidos à distância, prolongando, assim, o tempo de isquemia total (TIT). Os efeitos do TIT sobre a funçao cardíaca no pós-operatório imediato e a necessidade de agentes inotrópicos ainda sao controversos, devendo os limites de segurança serem determinados. As manifestaçoes do TIT no índice cardíaco, durante os primeiros três dias pós transplante cardíaco ortotópico (I/C 1-3), o período total do suporte inotrópico (SIT), a dose total/kg de dopamina e dobutamina (D+D/kg), a necessidade inotrópica máxima e picos dos níveis de CPK-MB (CPK-MB) foram medidos em 96 receptores de transplante cardíaco, na Universidade de Minnesota, para determinar a relaçao destas variáveis com o TIT. O TIT variou entre 61 e 288 minutos (média 171,7, D.P. 51,9). A populaçao foi dividida entre grupos representando intervalos de 30 minutos. Embora os níveis de CPK-MB fossem inferiores nos grupos de TIT menores, nao houve diferença nos parâmetros de funçao cardíaca, tempo de suporte e necessidade inotrópica. Concluímos que tempos de isquemia até cinco horas sao bem tolerados e que outros fatores, como funçao cardíaca do doador previamente à remoçao do órgao, ou possível dano isquêmico durante a remoçao, sao mais importantes na determinaçao da performance pós-operatória imediata.