- Email: [email protected]
To the Editor—Biological Pacemakers Exhibit Positive Chronotropic Response to Emotional Arousal
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Heart Rhythm, Vol 9, No 12, December 2012
Regarding point 3, the analysis of the two left ventricular ejection fraction (LVEF) subgroups was performed to show that LVEF is a fairly “blunt instrument” in predicting sudden cardiac death (SCD) and a better predictor of total mortality. We agree with Dr. Madias that serial assessments of LVEF are important, but, more importantly, as mentioned above, we believe that serial assessment of the risk for SCD with repeated noninvasive tests, such as microvolt T-wave alternans (MTWA), and/or invasive tests, such as electrophysiologic study (EPS), is just as important, especially considering the decreased predictive accuracy over time noted in the ABCD trial. Ultimately, we should approach SCD as we do breast cancer or coronary ischemia, for which serial risk assessment is routine. Regarding point 4, the 74 patients without an implantable cardioverter-defibrillator (ICD) were included in the 99 patients with two negative tests, and their likelihood of SCD was extremely low, as noted in the ABCD trial. To the best of our knowledge, none of the patients without an ICD presented with an episode of sustained ventricular tachycardia. Otto Costantini, Guy A. Amit, Dennis Super, David S. Rosenbaum,
MD MD MD MD
The Heart and Vascular Center MetroHealth Campus Case Western Reserve University Cleveland, Ohio
Reference 1.
Amit G, Rosenbaum DS, Super DM, Costantini O. Microvolt T-wave alternans and electrophysiological testing predict distinct arrhythmia substrates: implications for identifying patients at risk for sudden cardiac death. Heart Rhythm 2010;7:763–768.
To the Editor—Biological Pacemakers Exhibit Positive Chronotropic Response to Emotional Arousal We read Dr. Tseng’s editorial commentary1 regarding our article,2 and we thank her for the generally kind comments and insightful suggestions. However, there is one point we wish to clarify: we are criticized for not having pace-mapped the rhythms in the animals to verify the site of origin of the rhythms we analyzed for heart rate variability. In fact, as mentioned in the Methods section, we did pacemap all dogs: only in that way could we evaluate whether the autonomic response was that of the implanted pacemaker. We did not further emphasize that point because pace-mapping has been a routine part of the biological pacemaker studies published by the Rosen lab. Michael R. Rosen, MD [email protected] College of Physicians and Surgeons of Columbia University New York, New York Richard L. Verrier, PhD Beth Israel Deaconess Medical Center Harvard Medical School Boston, Massachusetts
References 1. 2.
Tseng G-N. Can biologic pacemakers respond to physiologic emotional arousal? Heart Rhythm 2010;7:1841–1842 Shlapakova IN, Nearing BD, Lau DH, Boink GJJ, Danilo P Jr, Kryukova Y, Robinson RB, Cohen IS, Rosen MR, Verrier RL. Biological pacemakers in canines exhibit positive chronotropic response to emotional arousal. Heart Rhythm 2010;7:1835–1840.
Heart Rhythm, Vol 9, No 12, December 2012
Regarding point 3, the analysis of the two left ventricular ejection fraction (LVEF) subgroups was performed to show that LVEF is a fairly “blunt instrument” in predicting sudden cardiac death (SCD) and a better predictor of total mortality. We agree with Dr. Madias that serial assessments of LVEF are important, but, more importantly, as mentioned above, we believe that serial assessment of the risk for SCD with repeated noninvasive tests, such as microvolt T-wave alternans (MTWA), and/or invasive tests, such as electrophysiologic study (EPS), is just as important, especially considering the decreased predictive accuracy over time noted in the ABCD trial. Ultimately, we should approach SCD as we do breast cancer or coronary ischemia, for which serial risk assessment is routine. Regarding point 4, the 74 patients without an implantable cardioverter-defibrillator (ICD) were included in the 99 patients with two negative tests, and their likelihood of SCD was extremely low, as noted in the ABCD trial. To the best of our knowledge, none of the patients without an ICD presented with an episode of sustained ventricular tachycardia. Otto Costantini, Guy A. Amit, Dennis Super, David S. Rosenbaum,
MD MD MD MD
The Heart and Vascular Center MetroHealth Campus Case Western Reserve University Cleveland, Ohio
Reference 1.
Amit G, Rosenbaum DS, Super DM, Costantini O. Microvolt T-wave alternans and electrophysiological testing predict distinct arrhythmia substrates: implications for identifying patients at risk for sudden cardiac death. Heart Rhythm 2010;7:763–768.
To the Editor—Biological Pacemakers Exhibit Positive Chronotropic Response to Emotional Arousal We read Dr. Tseng’s editorial commentary1 regarding our article,2 and we thank her for the generally kind comments and insightful suggestions. However, there is one point we wish to clarify: we are criticized for not having pace-mapped the rhythms in the animals to verify the site of origin of the rhythms we analyzed for heart rate variability. In fact, as mentioned in the Methods section, we did pacemap all dogs: only in that way could we evaluate whether the autonomic response was that of the implanted pacemaker. We did not further emphasize that point because pace-mapping has been a routine part of the biological pacemaker studies published by the Rosen lab. Michael R. Rosen, MD [email protected] College of Physicians and Surgeons of Columbia University New York, New York Richard L. Verrier, PhD Beth Israel Deaconess Medical Center Harvard Medical School Boston, Massachusetts
References 1. 2.
Tseng G-N. Can biologic pacemakers respond to physiologic emotional arousal? Heart Rhythm 2010;7:1841–1842 Shlapakova IN, Nearing BD, Lau DH, Boink GJJ, Danilo P Jr, Kryukova Y, Robinson RB, Cohen IS, Rosen MR, Verrier RL. Biological pacemakers in canines exhibit positive chronotropic response to emotional arousal. Heart Rhythm 2010;7:1835–1840.