[Cost-effectiveness of stress-only myocardial perfusion single photon emission computed tomography (SPECT) imaging]. / Evaluación de la perfusión miocárdica con tomografía computarizada por emisión de fotones individuales (SPECT) cardíaco: utilidad del protocolo sólo-estrés.

UNLABELLED: Single photon emission computed tomography (SPECT) myocardial perfusion imaging is widely used for diagnosing coronary artery disease (CAD). However, SPECT costs, imaging time, and radiation exposure, limit SPECT indications. OBJECTIVE: Determine whether a stress-only SPECT imaging would be enough to obtain a diagnosis of CAD improving nuclear laboratory efficiency. METHODS: 122 patients with unknown CAD were evaluated with stress-only SPECT imaging. In order to evaluate diagnostic accuracy and the prognostic value of the stress-only protocol, patients with abnormal SPECT underwent invasive angiography and patients with normal SPECT were followed-up during 3 years. RESULTS: Diagnosis time, SPECT cost, and radiopharmaceutical dosage were significantly lower as compared with the conventional SPECT imaging protocol (30, 40 and 55%, respectively). Diagnostic accuracy and cardiac prognosis information were comparable to those obtained with the conventional imaging protocol (positive predictive value for CAD of 85% and negative predictive value for cardiac events of 97%). CONCLUSIONS: In patients with intermediate risk for CAD, stress-only SPECT imaging will significantly improve nuclear laboratory efficiency, and with similar accuracy than that the one obtained with the conventional protocol.

Evaluation of ventricular synchrony with equilibrium radionuclide angiography: assessment of variability and accuracy.

BACKGROUND AND AIMS: Equilibrium radionuclide angiography (ERNA) has become an established method for assessing cardiac function. However, limited data are available to evaluate ventricular synchrony with ERNA. The aim of this study was to assess the variability and accuracy of ERNA to evaluate ventricular synchrony by means of phase images in healthy individuals and to compare them with a group of subjects with left bundle-branch block (interventricular dyssynchrony, LBBB) and with a group of patients with nonischemic, dilated cardiomyopathy (DCM) (inter- and intraventricular dyssynchrony). METHODS: The population was divided into groups as follows: group 1 included 22 healthy subjects, group 2 included 11 patients with LBBB and normal left ventricular ejection fraction (LVEF), and group 3 included 14 DCM patients with LVEF <35% and LBBB. Interventricular synchrony was measured as the difference between LV mean phase angle (mPA) and RV mPA (LV-RV mPA). Intraventricular synchrony for each ventricle was measured as the standard deviation (SD) of the RV mPA and LA mPA blood pools. RESULTS: Intra- and interobserver correlation coefficients were high for both inter- and intraventricular synchrony parameters. Area under the curve (AUC) was 0.98 for LV-RV mPA (p <0.001; 95% CI: 0.947-1.0). A cutoff value of 10 degrees yielded 96% sensitivity and 99% specificity to identify interventricular dyssynchrony. AUC was high for SD RV mPA and SD LV mPA (AUC = 1.0, p <0.001; 95% CI: 1.0-1.0 and AUC = 0.99, p <0.001; 95% CI: 0.979-1.0). A cutoff value of 22 degrees for SD LV mPA yielded 100% sensitivity and 100% specificity to identify LV intraventricular dyssynchrony. A cutoff value of 20 degrees for SD RV mPA yielded 100% sensitivity and 99% specificity to identify RV intraventricular dyssynchrony. CONCLUSIONS: ERNA is an accurate and highly reproducible technique for evaluation of ventricular function and synchrony.

[Chest pain syndrome in normal or non-diagnostic conventional ECG at the emergency service. Assessment with myocardial perfusion (SPECT) and ventricular function (Gated-SPECT)]. / El síndrome de dolor torácico en presencia de ECG convencional normal o no diagnóstico en el Servicio de Emergencia. Evaluación a través de la perfusión miocárdica (SPECT) y de la función ventricular (Gated-SPECT).

The arrival of a patient with chest pain syndrome (precordial) to the emergency represents a diagnostic challenge for the physician. Around 6 million persons are seen each year at the Emergency units in the USA. More than half of the patients are admitted for their cardiac evaluation. Its cardiac origin is confirmed in 10 to 15%, and about 15% of them develop myocardial infarction. However, 5 to 10% of patients are dismissed and develop myocardial infarction during the next 48 h. The diagnosis of the infarct is inadvertent and/or patients is not hospitalized in 2 to 8%. The mortality rate is duplicated in none hospitalized patients. Frequently, a conservative observation conduct and/or diagnostic expectation is taken, with the consequent saturation of the intensive care unit that looses its critical character and avoids quick mobilization of the patient with an increase in costs. The clinical judgment, a meticulous clinical history, and careful physical examination play a key role in the differential diagnosis of the precordial pain syndrome; however, pain can be atypical, absent or manifest as an equivalent of pain, which does not exclude the diagnosis of myocardial infarction or ischemia. Likewise, chest pain in the presence of a normal conventional ECG at rest, non-diagnostic or with minimal variations, does not rule out the possibility of a coronary obstruction and does not mean that the pain is not of coronary origin. Other characteristics of the ECG, such as T wave and ST segment alterations, bundle branch block (BBB), LV hypertrophy, interpretation discrepancies, can pose doubts or mistakes in the diagnosis. Although its diagnostic information is essential, other non-invasive laboratory tests are needed, such as the treadmill stress ECG, serial bioenzymatic markers, and myocardial perfusion scintigraphy (SPECT and Gated-SPECT) at rest or under physical or pharmacologic stress. The advantages and disadvantages of the stress ECG, the echocardiography, magnetic resonance and PET are mentioned. The advantages of the SPECT and Gated-SPECT in the diagnosis and prognosis are: 1) great diagnostic objectivity; 2) high sensitivity and specificity; 3) diagnosis does not depend on evolution time of the ischemia and/or infarction, since SPECT diagnoses the initial primary modifications of ischemia; 4) diagnosis is achieved within the established limit of time, in less than 4 to 6 hours. The designed protocols allow to obtain the diagnosis between 30 min and 1:30 h; 5) assesses the myocardium at risk; 6) stratifies the risk and prognosis; 7) defines the site and 8) the involved coronary artery(les); 9) provides the functional significance of the anatomic obstruction; 10) quantifies the ventricular function, i.e., ejection fraction, systolic and diastolic volumes, systolic thickening, ventricular failure signs; 11) provides three-dimensional visualization of the mobility of the left ventricular wall; 12) diagnoses simultaneously the associated presence of ischemia and/or infarction of the right ventricle; 13) its high negative predictive value allows to dismiss immediately and with a great safety margin those patients in whom SPECT revealed normal perfusion; 14) costs are reduced without adversely compromising the safety of the patients. We describe the algorithm used as guideline for the early diagnosis in the presence or absence of ischemic heart disease in the patient with precordial or chest pain syndrome with normal or non-diagnostic ECG at arrival to the emergency ward. It is necessary to modified the clinical educational patterns and to revaluate the advantages and limitations of the clinical history, physical exploration, as well as of the conventional ECG at rest and other diagnostic methods used specifically in relation to the chest pain syndrome with a normal or non diagnostic conventional ECG. SPECT and Gated-SPECT scintigraphy is considered as the best individual and isolated non-invasive test for the diagnostic solution of the precordial syndrome at the Emergency Unit.

Valoración simultánea de la perfusión y la viabilidad miocárdica a través del estudio de dos isótopos (talio reposo/MIBI esfuerzo). Experiencia inicial en México y América Latina / Simultaneous evaluation of myocardial perfusion and viability by means of two isotopes (thallium at rest and sestamibi during exercise). Initial experience in Mexico and in Latin America

La tomografía computada por emisión de fotón simple (SPECT) con MIBI en reposo/esfuerzo, tiene una sensibilidad y especificidad similar a la del SPECT de TL 201 para la detección de enfermedad de arterias coronarias. Sin embargo, El MIBI no es un agente ideal para estudiar la viabilidad miocárdica. No existe ningún artículo publicado en América Latina usando el protocolo de SPECT con dos isótopos para evaluar la perfusión y la viabilidad miocárdica. Estudiamos 44 pacientes consecutivos con enfermedad de arterias coronarias, 37 de ellos con infarto previo. A todos los pacientes se les hizo coronariografía previa, se inyectó una dosis de 3 mCi de TL 201 en reposo y, después, 25 mCi de MIBI durante el esfuerzo y se adquirió el estudio con técnicas SPECT. La imagen de esfuerzo se adquirió 30 minutos después del ejercicio físico o una hora después de la estimulación farmacológica con dipiridamol. Para validar los hallazgos de la perfusión, los pacientes regresaron al siguiente día para una inyección de 7 mCi de MIBI en reposo. Las imágenes obtenidas fueron evaluadas por dos observadores dividiendo el corazón en 20 segmentos para su análisis y para cada segmento se usó una escala de 5 puntos: 0= normal a 4= ausencia de captación. La concordancia de la puntuación de los segmentos entre el T1 201 y el MIBI en reposo y la comparación del porcentaje de los defectos reversibles y no reversibles entre ambos protocolos fue del 90.7 por ciento. Conclusiones: El estudio con dos isótopos en un método seguro para la evaluación de la enfermedad arterial coronaria. Mostró una buena concordancia con el protocolo de MIBI en reposo/esfuerzo, tanto para la valoración de los defectos de perfusión en reposo como de la reversibilidad y fue un método superior para evaluar la viabilidad miocárdica