Possible Contribution of Ischemia of the Conus Branch to Induction or Augmentation of Brugada Type Electrocardiographic Changes in Patients With Coronary Artery Disease

Abstract

SummaryRecent evidence suggests an association between vasospastic angina and Brugada syndrome. Here we present two cases of coronary artery disease who presented with ECG abnormalities which might have been provoked or enhanced by ischemia of the conus branch of the right coronary artery. The 12-lead ECGs demonstrated normal sinus rhythm in these two cases. Interestingly, a saddle back or coved type ST segment elevation in leads V1-V3 was documented either in the percutaneous transluminal angioplasty procedure of the proximal right coronary artery or with an intracoronary acetylcholine (Ach) administration into the right coronary artery. These Brugada type ECG changes were restored to the baseline ECG waveform after improvement in the ischemia. In the second case, vasospasms of the conus branch of the right coronary artery were associated with a coved type ST segment elevation in leads V1 to V2. We discuss the possible interaction between ischemia caused by conus branch lesions and Brugada type electrocardiographic changes. ( and Brugada syndrome has been reported in several cases. 1,2) According to Noda, et al, the coexistence of vasospastic angina and Brugada syndrome was not rare (11%) and they hypothesized that mild ischemia and vagal influences act additively with the substrate responsible for the Brugada syndrome reported in the literature. 1)When Brugada syndrome and vasospastic angina coexist, the risk of inducing life-threatening ventricular fibrillation caused by Brugada syndrome or coronary vasospasms would be high.3) On the other hand, the therapeutic strategy for the two diseases is quite different since Ca channel blockers may cause deteriorative effects in Brugada syndrome. In fact, Chinushi reported a case with Brugada syndrome and vasospastic angina in which there was shortening of the ventricular fibrillatory interval after the administration of verapamil.4) Thus, the interaction between Brugada type ECG abnormalities and vasospasms or ischemia is very important from the therapeutic point of view.It is well known that the conus branch of the right coronary artery supplies the right ventricular outflow tract, and there are some reports regarding ischemia caused by conus branch lesions that may have induced Brugada type ECG changes. 5) Recent experimental evidence has also suggested that acute global ischemia in right ventricular wedge preparations can cause a loss of the action potential dome, leading to ST-segment elevation similar to that in Brugada syndrome. 6) Furthermore, a recent paper has shown that the occurrence of a J wave in the 12-lead ECG may be a marker for acute ischemia. 7) In this paper, we present two cases with coronary artery disease who presented with ECG abnormalities which might have been provoked by ischemia of the conus branch of the right coronary arteries, and discuss the possible interaction between these two phenomena.

Ischemia-induced Brugada phenocopy

“…This lesion was distal to the origin of the conus branch and therefore not affecting flow through it. In experiments involving acetylcholine and ergonovine to induce coronary spasm; the Brugada phenotype (BrP) could be induced especially when spasm was provoked in the right coronary arteries [2,3]. Increase in outward currents (I to ) and/or decrease in inward currents (I Ca ) induced by ischemia were postulated to result in augmentation of ST-segment elevation in the right precordial leads.…”

Acute Myocardial Infarction with a Left Main Trunk Lesion and Documented Lambda-like J Waves

“…In our case, in addition to the main culprit lesion at segment 7 in the LAD, a 75% stenotic lesion in the LMT might also have played a critical role in the genesis of the ECG changes, since the specific features as described by Hirano et al almost matched our case. On the other hand, recent reports have provided evidence that ischemia of the conus branch may induce Brugada-type ECG changes in patients with coronary artery disease (19)(20)(21)(22). In our case, the Brugada-like ECG pattern may have been caused by a LMT lesion leading to possible conus branch ischemia.…”

Acute myocardial infarction with isolated conus branch occlusion

“…3,5 Matthews 5 reported that conus branch was occluded by injection to RCA during angiography. Eichhofer et al 4 reported that stent implantation in the right proximal coronary artery resulted in conus branch occlusion.…”

“…There are 2 reports of Brugada-like ECG changes due to conus branch vasospasms with acetylcholine, which resulted in ventricular fibrillation or ventricular tachycardia. 3,6 Because Brugada syndrome can lead to ventricular fibrillation, and thus sudden death, treatment of conus branch occlusion is of clinical importance. In our case, penetration of a guidewire was attempted, and blood flow was restored without development of ventricular fibrillation or tachycardia.…”