"Giant R wave" electrocardiogram pattern during exercise treadmill test: A case report
© Testa-Fernández et al; licensee BioMed Central Ltd. 2011
Received: 12 December 2010
Accepted: 11 July 2011
Published: 11 July 2011
The exercise treadmill test is widely used in the evaluation of patients with suspected or known coronary artery disease. The typical ischemic response used to be ST-segment depression.
We describe a case of a 51-year-old Caucasian man with an unusual ischemic response during the exercise treadmill test: a "giant R wave" electrocardiogram pattern as a manifestation of hyperacute ischemia that resolved with sublingual nitroglycerin. Coronary catheterization showed a severe stenosis in a proximal dominant circumflex coronary artery. We hypothesize that, in this case, the "giant R wave" pattern was related to severe hyperacute ischemia due to coronary spasm superimposed on the atherosclerotic lesion, which probably caused complete occlusion of the artery. The patient was successfully treated with coronary percutaneous revascularization.
This is a dramatic and rare ischemic response during the exercise treadmill test, in which, a rapid administration of nitroglycerin can prevent life-threatening events.
A typical ischemic response during an exercise treadmill test (ETT) is ST-segment depression. ST-segment elevation is present in only about 3.5% of patients who undergo this test  and is more specific for indicating the site of the culprit lesion [2, 3]. The "giant R wave syndrome" was first described by Prinzmetal et al.  in the context of variant angina, and it is characterized by the appearance of a giant R wave, loss of the S wave, and merging of the QRS complex with the ST segment, causing a monophasic QRS-ST complex in leads facing the ischemic territory. This pattern may be rarely observed following coronary artery occlusion in acute myocardial infarction (MI), following variant angina during an ETT (or spontaneously at rest), and after percutaneous transluminal coronary angioplasty or experimental coronary artery ligation . We report a case of a patient who developed the giant R wave syndrome during an ETT.
The giant R wave syndrome was first described by Prinzmetal et al.  in the context of variant angina. Since then, similar ECG changes have been recorded in percutaneous transluminal coronary angioplasty, experimental coronary ligation, and in patients who had an acute MI (in this latter case, infrequent documentation exists in association with inferior MI, probably because of the smaller size of ischemic injury as compared to the anterior MI, resulting in less impressive ECG changes) . The electrophysiological mechanism of the giant R waves in the setting of myocardial ischemia has been attributed by most investigators to the aberrant propagation of ventricular activation from the normal myocardium toward the ischemic area, in which there is a marked slowing of conduction velocity . In variant angina, ST-segment elevation can be provoked by exercise, hyperventilation, or cold stimulation in about 30% of patients . In our patient, the giant R wave pattern was provoked by exercise during ETT, which also showed nodal rhythm, and resolved with sublingual nitroglycerin administration. Coronary catheterization showed severe stenosis in a mid-dominant circumflex coronary artery, with an extensive territory at risk. We hypothesize that, in our patient, the giant R wave pattern was related to severe hyperacute ischemia due to a coronary spasm superimposed on the atherosclerotic lesion, which probably caused a complete occlusion of the artery. This severe ischemic response could explain the patient's prior symptoms due to cardiac rhythm and blood pressure abnormalities.
In this case report, we describe a dramatic, rare ischemic response during ETT that was probably caused by superimposition of a coronary spasm in a severe stenosis of a mid-dominant circumflex coronary artery. Rapid administration of nitroglycerin is crucial because it can prevent life-threatening events.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The authors thank the nurses for their cooperation.
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