Radionuclide imaging of myocardium with mental stress in the investigation of thoracic pain

Silva, Lívia Maria Lima da; Barbirato, Gustavo Borges; Drumond Neto, Cantídio; Nóbrega, Antonio Claudio Lucas da; Coimbra, Alexandro; Mesquita, Claudio Tinoco

doi:10.1590/S0066-782X2009001000024

Abstracts

Thoracic pain is a common symptom in emergency services, and stress radionuclide imaging represents one of the phases of risk stratification in these individuals. However, a group of patients with negative functional exams after physical or pharmacological stress develops myocardial ischemia during this psychological stress. Alterations in vascular tonus as a response to endogenous mechanisms are the physiopathologic basis for such alterations. We report a case that illustrates how mental stress radionuclide imaging has the potential to be used in the assessment of myocardial ischemia non-detected by conventional methods in patients with suspicion of ischemic thoracic pain.

Radionuclide Imaging; Psychological Stress; Myocardial Ischemia

A dor torácica é um sintoma comum nos serviços de emergência e a cintilografia de estresse representa uma das etapas da estratificação de risco nesses indivíduos. Entretanto, um grupo de pacientes com exames funcionais negativos após o estresse físico ou farmacológico desenvolve isquemia miocárdica durante estresse mental. As alterações do tônus vascular em resposta a mecanismos endógenos são a base fisiopatológica dessas alterações. Relata-se um caso que ilustra como a cintilografia de estresse mental tem o potencial para ser utilizada na avaliação de isquemia miocárdica, não detectada pelos métodos convencionais, em pacientes com suspeita de dor torácica isquêmica.

Cintilografia; Estresse Psicológico; Isquemia Miocárdica

El dolor torácico es un síntoma común en los servicios de emergencia y el centellograma de estrés representa una de las etapas de la estratificación de riesgo en estos individuos. No obstante, un grupo de pacientes con exámenes funcionales negativos después del estrés físico o farmacológico desarrolla isquemia miocárdica durante el estrés mental. Las alteraciones del tono vascular en respuesta a mecanismos endógenos son la base fisiopatológica de estas alteraciones. Se relata un caso que ilustra cómo el centellograma de estrés mental tiene potencial para ser utilizado en la evaluación de isquemia miocárdica, no detectada por los métodos convencionales, en pacientes con sospecha de dolor torácico isquémico.

Centellograma; estrés psicológico; isquemia miocárdica

CASE REPORT

Universidade Federal Fluminense, Hospital Universitário Antônio Pedro (HUAP); Hospital Pró-Cardíaco, Rio de Janeiro, RJ, Brazil

Mailing address

SUMMARY

Thoracic pain is a common symptom in emergency services, and stress radionuclide imaging/ represents one of the phases of risk stratification in these individuals. However, a group of patients with negative functional exams after physical or pharmacological stress develops myocardial ischemia during this psychological stress. Alterations in vascular tonus as a response to endogenous mechanisms are the physiopathologic basis for such alterations. We report a case that illustrates how mental stress radionuclide imaging has the potential to be used in the assessment of myocardial ischemia non-detected by conventional methods in patients with suspicion of ischemic thoracic pain.

Keywords: Radionuclide Imaging; Psychological Stress; Myocardial Ischemia.

Introduction

In the emergency room, thoracic pain represents a hard-diagnosis entity. This difficulty results in inadequate discharge of carriers of myocardial ischemia syndrome (MIS), who will remain untreated and vulnerable to morbid events. Imaging exams have been playing an important role in the stratification of risk in patients that are suspected to be carriers of myocardial ischemia. Among the most widely used exams, radionuclide imaging is the one that bespeaks the most its value in diagnostic and prognostic evaluation of patients with thoracic pain¹. Despite the fact that a radionuclide myocardial perfusion imaging is frequently associated with a risk for adverse events lower than 1% per year², some patients with coronary arterial disease only have manifestation of ischemia when submitted to non-conventional ischemia induction techniques, such as psychological stress³. While the basis for the induction mechanism for perfusion alteration of radionuclide imaging during physical activity with intravenous dipyridamole is coronary vasodilatation, psychological stress causes epicardial coronary and microvascular vasoconstriction in patients with endothelial dysfunction and/or arteriosclerosis⁴. The use of radionuclide imaging in a patient under psychological stress and negative investigation for myocardial ischemia in the emergency room by conventional methods has not been described yet.

Case report

Female patient, 68 years old, Caucasian, was admitted in the emergency service with low intensity precordial discomfort in repose with duration superior to 30 minutes and associated with dyspnea and palpitations. The patient related similar previous episodes without diagnosis.

The physical exam identified no alterations, presenting blood pressure (BP) and heart rate (HR) discretely elevated (BP = 140 x 90 mmHg and HR = 88 bpm). Twelve-derivation electrocardiography showed diffuse unspecific alterations in ventricular repolarization, and myocardial necrosis markers' dosage was normal. Transthoracic echocardiography analysis revealed debt in the left ventricle (LV) relaxation and absence of global or segmental systolic dysfunction of LV. After the hypothesis of myocardial infarction was rejected, the patient was submitted to stratification with radionuclide imaging of myocardial perfusion after physical stress and in rest, with utilization of ^99mTc-Sestamibi. One-day protocol was applied, initially in repose. In stress phase, the patient was submitted to ergometric test under run-away protocol (VO₂ maximum 36.75 ml/kg.min; Test duration: 11 min 12 sec; MET maximum: 10.5; FC maximum: 159 bpm e MVO₂ maximum: 31.54 ml O₂ 100g VE/min). The image was acquired approximately 90 minutes after the test. No perfusion, contractility or myocardial thickness defects were observed during exam (Figure 1). The patient was discharged asymptomatic and, thus, without a diagnosis for the described symptoms. Afterwards, she was referred to radionuclide imaging with sensorial stress, and application of Stroop method, which is an information processing test that employs the conflict word/color. This method consists of the appearance of successive images in a computer as the patients says out loud the name of the color of the visualized letters and listens to other color names in a headphone, which generates an hearing conflict⁵. During the exam, blood pressure was monitored continually and non-invasively by means of digital infrared photopletismography simultaneously to continuum derived 12-lead electrocardiographic assessment. ^99mTc-Sestamibi was injected at the moment of maximum stress (2.5 minutes of protocol). Stress induction had a maximum duration of five minutes, and the respective image was obtained 60 minutes later with posterior comparison to previous repose period. There was no symptoms reproduction or electrocardiography alteration during sensorial stress. An effective hemodynamic response to stress was observed, with variation of: systolic blood pressure: + 43 mmHg (VR: 10-25 mmHg); diastolic blood pressure: +22 mmHg (VR: 5-15 mmHg); and heart rate: + 7 mmHg (VR: 5-15 mmHg). Radionuclide imaging of psychological stress demonstrated reversible perfusion defects in the segments concerning the anterior and inferior walls, interventricular apex and septum, as shown in Figure 2, results that suggest sensorial stress-induced myocardial ischemia.

The presence of sensorial stress-induced ischemic alterations motivated an anatomic evaluation through coronarygraphy, which showed a 40% lesion in the medium portion of anterior descending coronary artery, 30% lesion in the proximal portion of the second diagonal artery and 40% lesion in the proximal portion of the right coronary artery. An optimized medical treatment with ambulatory follow-up was chosen.

Discussion

One of the advantages of radionuclide imaging with myocardial perfusion is the revelation of presence of ischemia in patients who did not present obstructive coronary disease⁶. The presence of stress-induced myocardial ischemia in patients with atypical anginous thoracic pain, but without obstructive coronary disease, is frequently associated with endothelial dysfunction⁷. Several experimental studies have contributed to a better understanding on the association between psychological stress and myocardial ischemia, with emphasis given to the Psychophysiological Interventions in Myocardial Ischemia (PIMI) study, in which the different responses to physical and psychological stress of carriers of coronary arterial disease and the association of psychological stress ischemia with mortality are documented⁸. Psychological stress unleashes an increase in heart rate and in blood pressure, which are measured through stimulation of adrenergic sympathetic activity. In healthy individuals, the integer endothelium promotes a compensatory vasodilator response to sympathetic stimulus. In carriers of coronary arterial disease, whose physiopathologic basis is the endothelial dysfunction, this compensatory mechanism is damaged, which leads to a significant coronary vasoconstriction and to alterations in the myocardial offer and demand of oxygen⁹. An inappropriate response may cause ventricular contraction dysfunction, myocardial ischemia or cardiac rhythm disorders⁹. Due to physiopathologic differences between physical, pharmacological and psychological stress, individual variations in the response to each stimulus are expected. Studies that assessed the genetic variability as polymorphism of β1-adrenergic receptors, in which patients possessed Ser49 allele homozygosis, demonstrated up to the triple of ischemia cases¹⁰. In practice, this fact influences the observation of individuals without ischemia that is detectable by conventional stress methods, presenting positivity only after submission to psychological stress. Such fact demonstrates the applicability of this stress modality for the detection of underdiagnosed cases of myocardial ischemia in thoracic pain manifestations. In the abovementioned clinical case, the patient were under stress and had incipient coronary artery disease, but without significant obstruction of arterial light. The patient presented ischemic alterations in the radionuclide imaging only when submitted to psychological stress through Stroop Color method, which consolidates a cardiac etiology for the observed alterations. These data suggest a potential applicability of psychological stress as complementation of myocardial ischemia investigation in patients that present thoracic pain of inexplicable etiology. More studies are currently being conducted for the investigation of this new applicability of stress radionuclide imaging.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Sources of Funding

There were no external funding sources for this study.

Study Association

This article is part of the thesis of master submitted by Gustavo Borges Barbirato, from Hospital Pró-Cardíaco e Universidade Federal Fluminense - Hospital Universitário Antônio Pedro.

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