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LETTER TO THE EDITOR

To the Editor,We read with great interest the advance publication of Dr.

Gami et al.1 on the successful ablation of an atrial tachycardiain the right coronary cusp of the aortic valve. We congratulatethe authors for a very interesting case of atrial fibrillation thatcould be ablated within the aorta. We agree with the authorsthat their case suggests a region of remote atrial muscula-ture electrically connected to the atrium as the actual ablatedarrhythmogenic substrate. However, we believe that the suc-cessful ablation site was probably located in the noncoronarycusp of the aorta (NCC) rather than the right coronary cusp(RCC). We base our opinion on several observations. First,in the cardiac tracings from the successful ablation site, thelocal atrial electrogram was greater in amplitude than theventricular electrogram. In addition, the atrioventricular am-plitude ratio was greater in the distal electrode pair than in theproximal electrode pair of the ablation catheter, even thoughthe distal electrode pair would have been closer to the ven-tricular myocardium had the tip of the ablation catheter beenlocated within the right coronary cusp. In our experience ofmapping the aortic sinus cusps,2-4 we have never observedsuch findings in the RCC probably because, anatomically,the atrioventricular groove is normally located at the junctionbetween the RCC and NCC.5 Mapping of the RCC typicallydemonstrates a greater ventricular electrogram amplitude themore distally the catheter is placed into the cusp. In the car-diac tracings exhibiting pacing from the NCC, the amplitudeof the local ventricular potential was greater in the proximalelectrode pair than in the distal electrode pair of the abla-tion catheter, probably because the proximal electrode pairof the ablation catheter was located in the RCC while the dis-tal electrode pair was within the NCC. Indeed, placement ofthe tip of an ablation catheter into the NCC usually requiresthat the proximal curve on the catheter be angled anteriorlywhere it is often located within the RCC. However, a dis-sociated far-field atrial electrogram was recorded from onlythe distal electrode pair in the NCC. Therefore, we believethat the successful ablation site must have been located in theNCC rather than the RCC. Second, the intracardiac echocar-diographic image that is presented may have demonstratedthat the shaft of the ablation catheter was located in the RCCwhile the tip was in the NCC. A more convincing figure

doi: 10.1111/j.1540-8167.2008.01213.x

would have simultaneously imaged both the RCC and theNCC.

The authors suggested that the atrial tachycardia originwas located in the myocardium within the RCC. However,even if the successful ablation site was located exactly in theRCC, that description is misleading. For the greater part, thecoronary aortic sinuses are made up of the wall of the aorta.5,6

At the base of each of those coronary sinuses, however, acrescent of ventricular musculature is incorporated as part ofthe arterial segment and plays a role as a hinge of the valvularleaflets. That does not happen within the noncoronary sinus.This is because the base of that sinus is exclusively fibrousdue to the continuity between the NCC and the anterior leafletof the mitral valve. Therefore, it would be proper to think thatthere is no atrial musculature in any of the coronary cusps.

TAKUMI YAMADA, M.D., PH.D.G. NEAL KAY, M.D.

Division of Cardiovascular DiseaseUniversity of Alabama at Birmingham

E-mail: takumi-y@fb4.so-net.ne.jp

References

1. Gami AS, Venkatachalam KL, Friedman PA, Asirvatham SJ: Suc-cessful ablation of atrial tachycardia in the right coronary cusp ofthe aortic valve in a patient with atrial fibrillation: What is the sub-strate? J Cardiovasc Electrophysiol Published article online: 21-Feb-2008. doi:10.1111/j.1540–8167.2007.01094.

2. Yamada T, Huizar JF, McElderry HT, Kay GN: Atrial tachycardia origi-nating from the noncoronary aortic cusp and musculature connection withthe atria: relevance for catheter ablation. Heart Rhythm 2006;3:1494-1496.

3. Yamada T, McElderry HT, Doppalapudi H, Kay GN: Catheter ablationof ventricular arrhythmias originating from the vicinity of the His bun-dle: Significance of mapping of the aortic sinus cusp. Heart Rhythm2008;5:37-42.

4. Yamada T, Yoshida N, Murakami Y, Okada T, Muto M, Murohara T,McElderry HT, Kay GN: Electrocardiographic characteristics of ventric-ular arrhythmias originating from the junction of the left and right coro-nary sinuses of Valsalva in the aorta: The activation pattern as a rationalefor the electrocardiographic characteristics. Heart Rhythm 2008;5:184-192.

5. McAlpine WA: Heart and Coronary Arteries. New York: Springer-Verlag, 1975.

6. Anderson RH: Clinical anatomy of the aortic root. Heart 2000;84:670-673.