Asystole During Exercise Stress Test: Analysis of Cardioinhibitory Response

International Journal of Cardiovascular Sciences. 2016;29(3):236-238 236

CASE REPORT

Asystole During Exercise Stress Test: Analysis of Cardioinhibitory Response Luis Sérgio Carvalho Luciano, Fabrício Bonotto Mallmann, Daniel Medeiros Moreira, Gabriela Nassar Frederico, Maíra Fracasso Instituto de Cardiologia de Santa Catarina – São José, SC – Brazil

This is the case of asystole during stress test at the arrest (CRA) in asystole (Figure 1) lasting 20 seconds stage of physical stress in a 30-year-old man with in the fifth minute of the test. Immediately submitted previous history of syncope. The episode was related to a to cardiopulmonary resuscitation (CPR), followed by cardioinhibitory response with asystole during the exercise endotracheal intubation with reversion to sinus rhythm. test stress stage, which is not frequent in the literature. Post-PCR electrocardiogram showed signs of ischemia on the inferior wall. Transthoracic echocardiogram Introduction performed afterwards revealed global preserved segmental contractility without structural abnormalities. Episodes of vasovagal reaction are described as part The patient was sent by plane to Instituto de of the main complications during exercise test and may Cardiologia de Santa Catarina (ICSC), a state reference for range from a brief episode of hypotension to extreme high complexity cardiology cases. Soon after admission, cases, translated by asystole. the patient underwent coronary angiography, which Cardiac asystole related to exercise in patients without showed the circumflex artery originating from the right structural heart disease is uncommon in clinical practice.1 coronary artery (Figure 2) and absence of obstructive In the literature, cases of asystole most often occur outside lesions. Chest computed tomography angiography the period of stress, most commonly in the recovery stage showed no signs of pulmonary thromboembolism. of the exercise test. Myocardial perfusion scintigraphy with technetium We report the case of a young patient without a produced images after pharmacological stress with structural cardiac disease who presented cardiac asystole dipyridamole and at rest, which showed no signs of in the stress stage of the exercise test. ischemia or myocardial fibrosis and showed normal left ventricular function (left ventricular ejection Case Report fraction = 65%). Permanent pacemaker implantation was chosen due to prolonged asystole requiring CPR during Hypertensive, dyslipidemic 30-year-old man with the stress stage of the exercise test. The patient progressed obstructive sleep apnea and grade III obesity (BMI = well and was referred to outpatient follow-up. 41 kg/m²). The patient reported an episode of syncope during exertion 13 days before the exercise stress test. Discussion Electrocardiogram at rest showed sinus rhythm with no significant abnormalities. During the exercise test, the The prevalence of anomalous origin of the circumflex patient showed no signs of ischemia or tachyarrhythmia. artery is around 0.6% and is associated with increased The patient presented Mobitz II 2nd degree atrioventricular incidence of myocardial ischemia and sudden death, block (Figure 1) and evolved with cardiorespiratory especially among athletes.2,3 The most common complications related to exercise testing include serious tachyarrhythmia (4.78/10,000 tests), Keywords infarction (3.58/10,000 tests) and deaths (0.5/10,000 tests).4 Exercise test; Syncope; Bradycardia. Asystole during exercise in young people without any heart

Mailing Address: Luis Sérgio Carvalho Luciano Rua Adolfo Donato da Silva, s/n – Praia Comprida. Postal Code: 88103-901 – São José – SC – Brazil E-mail: [email protected]

DOI: 10.5935/2359-4802.20160026 Manuscript received on February 15, 2016; revised on April 29, 2016; approved on April 24, 2016. Luciano et al. Int J Cardiovasc Sci. 2016;29(3):236-238 237 Asystole During Stress Test Case Report

Figure 1 Mobitz II 2nd degree atrioventricular block progressing to asystole.

Figure 2 Circumflex coronary artery originating from the right coronary artery.

disease is described as a rare event in the literature and it contraction with activation of mechanoreceptors on the is believed that one of the main mechanisms responsible ventricular wall and consequent response of the afferent is a vasovagal component with increased vagal stimulus.5 vagus nerve. This vagal stimulus can trigger a sudden The mechanisms responsible for syncope and asystole in withdrawal of sympathetic efferent activity (negative patients with anomalous origin of the circumflex artery circular feedback) and increase the parasympathetic efferent are unknown, but possibly the same ones present in tone with vasodilatation and subsequent hypotension. patients without a structural disease: bradycardia occurs Hypotension usually precedes bradycardia, hence the by a gradual reduction in the end-diastolic and end-systolic inactivation of the sympathetic efferent and consequent volumes, with maximum increase in fractional shortening vasodilation may be the primary mechanism of syncope. before syncope. Increased sympathetic tone in the scenario Bradycardia and asystole as markers of increased of a relatively empty heart leads to vigorous myocardial parasympathetic tone would play only a secondary role Int J Cardiovasc Sci. 2016;29(3):236-238 Luciano et al. Case Report Asystole During Stress Test 238

in most patients with vasodepressor syncope and may Luciano LSC, Mallmann FB, Moreira DM, Frederico GN, even prevent the pacemaker from avoiding hypotension Fracasso M. and syncope in most patients; however, cardioinhibition with consequent bradycardia or asystole may be the Potential Conflicts of Interest primary mechanism in some patients.5 This study has no relevant conflicts of interest.

Author contributions Sources of Funding Conception and design of the research:Luciano This study had no external funding sources. LSC, Mallmann FB. Acquisition of data:Luciano LSC, Mallmann FB, Moreira DM, Frederico GN, Fracasso M. Writing of the manuscript:Luciano LSC, Moreira DM. Academic Association Critical revision of the manuscript for intellectual content: This study is not associated with any graduate programs.

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2. Page HL Jr, Engel HJ, Campbell WB, Thomas CS Jr. Anomalous origin 5. Osswald S, Brooks R, O’Nunain SS, Curwin JH, Roelke M, Radvany of the left circumflex coronary artery. Recognition, angiographic P, et al. Asystole after exercise in healthy persons. Ann Intern Med. demonstration and clinical significance. Circulation. 1974;50(4):768-73. 1994;120(12):1008-11. 3. Yamanaka O, Hobbs RE. Coronary artery anomalies in 126,595 patients undergoing coronary arteriography. Cathet Cardiovasc Diagn. 1990;21(1):28-40.