Negative Contractile Reserve With Low-Dose Dobutamine in Patients With Ischemic Cardiomyopathy Investigated by Gated Myocardial Perfusion SPECT

Introduction and objectivesTo investigate negative contractile responses in the left ventricle during low-dose dobutamine (LDD) gated single-photon emission computed tomography (SPECT) in patients with ischemic cardiomyopathy.MethodsSixty-eight consecutive patients (mean age, 60 [11] years; 7 male) with ischemic cardiomyopathy (ie, left ventricular ejection fraction [LVEF] ≤40%) were evaluated using gated-SPECT at rest and during LDD infusion. Associations between a negative contractile reserve (ie, a ≥1-grade improvement in wall thickening score with LDD infusion) and scintigraphic viability criteria and coronary angiography findings were analyzed.ResultsSome 42.6% (29/68) of patients had a negative contractile reserve in one or more segments. In 14.7% (n=10), the LVEF decreased by ≥4% with LDD. These patients had more segments with a negative contractile reserve (2.8 [2.5] vs 0.87 [0.40]; P=.042), and the cut-off value on receiver operating characteristic curve analysis was ≥2 segments with a negative contractile reserve (sensitivity 70%, specificity 74%, positive likelihood ratio 2.71, negative likelihood ratio, 0.40). Some 94% (74/79) of segments with a negative contractile reserve were in viable myocardium (ie, normal or viable on scintigraphy). Twelve of 17 segments with akinesia or severe hypokinesia and a negative contractile reserve satisfied scintigraphic viability criteria, with the majority (10/12) lying in territories supplied by a patent coronary artery.ConclusionsA negative contractile reserve was not uncommon in patients with ischemic cardiomyopathy and was associated with a general decrease in left ventricular systolic function. It was observed mainly in myocardial segments that appeared viable on scintigraphy and were supplied by a patent coronary artery.

Introducción y objetivosAnalizar la respuesta contráctil negativa (RCN) del ventrículo izquierdo (VI) en la gated-SPECT con bajas dosis de dobutamina (BDD) en pacientes con miocardiopatía isquémica (MI).MétodosSe estudió prospectivamente a 68 pacientes (media de edad, 60 ± 11 años; 7 mujeres) con MI mediante gated-SPECT en reposo y durante la infusión de BDD. Se relacionó la RCN (aumento de la puntuación del engrosamiento ≥1 unidad) con los criterios gammagráficos de viabilidad y los resultados de la coronariografía.ResultadosEl 42,6% (29/68) de los pacientes presentó uno o más segmentos con RCN. En el 14,7% (n = 10) de los pacientes se observó una disminución de la fracción de eyección ≥ 4% con las BDD. Estos pacientes se caracterizaron por tener un mayor número de segmentos con RCN (2,8 ± 2,5 frente a 0,87 ± 0,4; p = 0,042), con un valor de corte en el análisis de curva ROC ≥2 segmentos con RCN (sensibilidad, 70%; especificidad, 74%; +LR, 2,71; −LR, 0,40). El 94% (74/79) de los segmentos con RCN correspondía a miocardio vivo (normal o viable gammagráficamente). De los 17 segmentos con acinesia o hipocinesia severa y RCN, 12 (71%) tenían criterios gammagráficos de viabilidad y en su mayoría (10/12) correspondían a territorios con arteria coronaria abierta.ConclusionesLa RCN no es un fenómeno infrecuente en los pacientes con MI y se relaciona con una disminución de la función sistólica general del VI. Mayoritariamente se observa en segmentos con criterios gammagráficos de viabilidad y dependientes de una arteria coronaria abierta.