Abstract. Rhythmic heart rate variability signifies a state of cardiovascular health. Loss of heart rate variability increases mortality and morbidity. Strategies that increase beat-to-beat variability include standard medical interventions such as beta blockers. Relaxation, meditation, and music therapy are non-traditional approaches that have been proposed to improve health. Several studies indicate that these alternative methods decrease heart rate and blood pressure. To date, little is known about the impact of music on the autonomic tone of the heart and heart rate variability. We hypothesize that music improves heart rate variability by decreasing cardiac sympathetic tone. In order to assess the effects of music, we used cardiac electrophysiologic studies (EPS) to acquire the sinus node recovery time (SNRT), sino-atrial conduction time (SACT), and A-A interval (AA) in patients exposed to live harp music in the EP lab. The following are preliminary results of our first three study patients. We observed that following exposure to music, these patients show improvement in SNRT, SACT, and AA compared to baseline measurements. These results suggest that the positive effects of exposure to music on heart rate variability are due to changes in autonomic tone.

Background
The concept of heart rate variability (HRV) has become a major determinant in cardiovascular health and prognosis.¹ Factors that lead to inappropriate activation of the sympathetic nervous system can be expected to adversely affect patient outcome, and factors that augment parasympathetic vagal tone tend to improve outcome. HRV is becoming more recognized as a risk predictor for cardiovascular disease. In one study, low HRV was the single most important predictor of a high risk of sudden death or serious arrhythmia.² The landmark Framingham Heart Study also supported the association between HRV and a decrease in all-cause mortality and cardiac events.^3,4 More recently, the ATRAMI study (Autonomic Tone and Reflexes After Myocardial Infarction) confirmed that both HRV and baroreflex sensitivity were independent predictors of cardiovascular mortality.⁵ Interestingly and more well known is the fact that fetal monitoring for HRV during the peri-partum period demonstrates the overall well being of the fetus.

Music has been reported to decrease heart rate and blood pressure in multiple studies in the neonatal population up to the adult population.^6,7 Specifically, in ventilated patients, music was shown to effectively decrease anxiety, heart rate and respiratory rate.⁸ Music was shown to decrease sedative requirements during surgery under spinal anesthesia.⁹ Within 72 hours of acute myocardial infarction, studies have shown that patients benefit from music therapy in regards to reductions in heart rate, respiratory rate, myocardial oxygen demand,¹⁰ and improvement in overall anxiety.¹¹ After coronary artery bypass graft surgery (CABG), music therapy was shown to improve the relaxation response by reducing anxiety, improving mood, and lowering heart rate and blood pressure.¹²

The work of both artists and chaos theorists has been influenced by HRV. For example, geometric patterns and musical compositions have been created by chaos theorists using electrocardiogram tracings for the original design. Cardiac electrophysiologist and chaos theorist Ary Goldberger, MD, and musical composer Zach Goldberger used a mathematical process called binning to translate the beat-to-beat variations of electrocardiograms into musical compositions.¹³ The electrocardiograms of healthy hearts translated into beautiful music with rhythmic variations, whereas monotone music lacking variation matched more closely with electrocardiograms from sick hearts. Another study examined 24-hour electrocardiograms from healthy subjects and transformed the heart period tachograms into binary symbol sequences.¹⁴ These sequences were found to share the same rhythmic patterns found in the time lines of African music indicating that heart period patterns, in particular those occurring during night sleep, can be interpreted as musical rhythms.

Few studies have investigated the specific changes of HRV in response to music. One study of eight patients showed that classical music decreased the sympathetic nervous system activation.¹⁵ Other interventions such as meditation, exercise, tai chi, and sauna therapy have been investigated as well as to their effects on cardiovascular outcomes. We propose that music improves HRV by modulating the autonomic tone of the heart.

Study Design
This is a prospective study, wherein subjects with underlying cardiac rhythm disturbances scheduled to undergo an electrophysiology study were enrolled. Study variables were measured before music (baseline), following five minutes of Canon in D by Johann Pachelbel (1653-1706) played on the harp, and five minutes following the music. This study was submitted to and approved by the institutional review boards at Carle Foundation Hospital and the University of Illinois, Urbana.

Subjects were ambulatory, non-institutionalized men and women, over the age of 18 years, with their primary cardiac rhythm originating from the sinoatrial node. Patients were excluded if they had recent myocardial infarction, percutaneous coronary intervention, or bypass in the past 30 days. Patients also were excluded if they had taken anti-arrhythmic agents, beta-blockers, calcium channel blockers or digitalis in the prior 48 hours before the study. After informed consent was obtained, subjects meeting the criteria were enrolled.

To date, fourteen patients have enrolled and participated. The study participant s demographic information and medical record is reviewed. Additional questions regarding health history, cardiopulmonary symptoms, physical activity, relaxation techniques, and current medications are asked. Each subject enrolled in the study serves as their own control during the EP testing. The baseline data is compared to data collected during the musical intervention and five minutes post-musical intervention.

The measurements include: heart rate, determined by EP recording strips; systolic and diastolic blood pressures, determined by a noninvasive automatic oscillometric blood pressure cuff hard-wired to the cardiac EP equipment; respiratory rate per minute, determined by manual measurement of the number of respirations in 30 seconds and multiplied by 2; oxygen saturation, determined by a noninvasive pulse oximetry monitor placed on the subject s finger; and myocardial oxygen demand, determined by using the rate pressure product, calculated by multiplying heart rate by systolic blood pressure.^16,17 Other parameters more specific to the electrical system of the heart include: RR, AA, AH, and HV conduction intervals, SACT, SNRT, and effective refractory periods.

Results
Demographic information on three patients is provided in Table 1. As evident in Table 2, there is a trend towards a decrease in sinus rate during the musical intervention. This trend was observed to persist for five minutes after the musical intervention. Specifically, the AA interval increases in length (Table 2). There is also a trend towards a significant decrease in SACT that persists during both the musical intervention and five minutes following music exposure. In addition, there is an increase in SNRT during music, but the effect seems to diminish rather quickly post musical intervention. We have also observed increases in the Wenckebach cycle length, both anterograde and retrograde. Qualitatively, less atrial and ventricular ectopy has been noticed during musical intervention.

Discussion
Our results show a slowing of the sinus node rate, as measured by the A to A interval. There is a notable increase in sinus node recovery time and a decrease in sino-atrial conduction time. These findings are consistent with decreased sympathetic tone and possibly augmented parasympathetic tone. The persistence of these changes five minutes after music exposure is intriguing.

Patients experience varying levels of sedation during the course of the EPS including the period that they are exposed to music. The medications used are mostly midazolam, diphenhydramine, and fentanyl. By achieving a conscious level of sedation, the patient s thoughts or biases about the piece of music, Pachelbel s Canon in D, are not emphasized. This helps to lessen the effect of the mind when a piece of music is heard, and let the music speak for itself.

Conclusion
The public is more aware of non-traditional or complimentary therapies to improve cardiovascular health. The effects of exercise, a healthy diet, medical therapy, and risk factor reduction are emphasized by physicians throughout the world. The effects of stress reduction are caught in a crossfire reducing stress is often recommended, yet little instruction is communicated by physicians on how to achieve this goal. Just as we routinely recommend exercise and healthy eating habits to our patients, we should consider providing specific recommendations for reducing stress and creating a cardiac relaxation response. The results presented in this report indicate that listening to classical music is one such recommendation for physicians to consider for their patients to achieve a cardiac relaxation response. As we expand the size of this study and the trends become more evident, we plan to share the additional study data. Further studies would include evaluating different types of music, different instruments, and live versus recorded music, as well as the frequency of exposure to music required for sustainable health benefits.

Acknowledgment. This study was approved by the Institutional Review Boards of the University of Illinois at Urbana/Champaign and the Carle Foundation Hospital. We greatly appreciate the assistance of the staffs of the electrophysiology lab and the prep recovery room at the Carle Heart Center for their support.