CLINICS 2010;65(9):927-929 LETTER TO THE EDITOR DOI:10.1590/S1807-59322010000900017 Cheyne-stokes respiration associated with hypertrophic cardiomyopathy and normal left ventricular ejection fraction Rodrigo P. Pedrosa,I Luciano F. Drager,I Murillo O. Antunes,II Edmundo Arteaga,II Geraldo Lorenzi-FilhoI I Sleep Laboratory, Pulmonary Division, Heart Institute (InCor), Hospital das Cl´ınicas, Faculdade de Medicina, Universidade de S a˜o Paulo, Sa˜ o Paulo, SP, Brazil. II Cardiomyopathy Medical Unit, Heart Institute (InCor), Hospital das Cl´ınicas, Faculdade de Medicina, Universidade de Sa˜ o Paulo, S a˜o Paulo, SP, Brazil. Email: geraldo.lorenzi@incor.usp.br Tel.: 55 11 3069-5486 INTRODUCTION Cheyne-Stokes respiration (CSR) is a form of periodic breathing in which central apneas and hypopneas alternate with periods of hyperventilation, producing a waxing and waning pattern of tidal volume. This brief case described an interesting association of CSR and hypertrophic cardiomyo- pathy (HCM) in a patient with normal left ventricular ejection fraction, providing physiological insights for the genesis of CSR. CASE DESCRIPTION A 64-year-old male patient was admitted for a routine cardiac evaluation with complaints of witnessed apnea during sleep. He had previous history of HCM and permanent atrial fibrillation. He was on regular use of carvedilol 50 mg/d; enalapril 40 mg/d, furosemide 80 mg/ d and warfarin 5 mg/d and was on NYHA stage III heart failure. Echocardiography demonstrated interventricular septum wall thickness of 20 mm and posterior wall thickness of 11 mm, without left ventricle outflow tract obstruction. The left ventricle ejection fraction was in the normal range (69%). The right ventricle systolic pulmonary pressure was 35 mmHg. Echocardiographic diastolic func- tion evaluation was impaired due to atrial fibrillation. Technetium (99mTc) radionuclide ventriculography showed normal biventricular systolic function and a median pulmonary transit time of 13 seconds (normal ,10 seconds), denoting diastolic dysfunction. Cardiac nuclear magnetic resonance also demonstrated normal global biventricular function. Arterial blood gas while awake showed pH:7.41; pCO2:33 mm Hg; paO2: 78 mm Hg; Sat: 97%; HCO3: 20.6 mMol/L; BE: -2.6 mMol/L. A full-overnight polysom- nography indicated a sleep efficiency of 95% with pre- dominantly light sleep (9.9% of stage 1, 75.9% stage 2, 4% of delta sleep (non REM stage 3/4) and 10.2% stage REM). The study showed an apnea-hypopnea index of 34.3 events per hour divided in: obstructive apneas = 8; central apneas = 12.1; mixed apneas = 5.3 and hypopneas = 8.9 events/ Copyright 2010 CLINICS – This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 927 hour. CSR pattern of breathing was present during the entire night (Figure 1). The respiratory pattern character- istics were averaged over 10 consecutive cycles of apnea at stage 2 sleep and the results are presented as mean¡SD. Hyperpnea duration was 42¡3 seconds (calculated as the time between the beginning of inspiration during the ventilatory cycle and the onset of the subsequent apnea). Apnea duration was 19¡3 seconds (defined as the time between the end of inspiration of the breath preceding a central apnea and the onset of inspiration of the breath terminating the apnea) resulting in a cycle duration of 62¡5 seconds (calculated as the sum of the hyperpnea and apnea durations). The circulation time from the lungs to the peripheral chemoreceptors was increased (29¡2 seconds- estimated by measuring the lung-to-ear circulation time [LECT]), which is the time from the first breath after a central apnea to the subsequent nadir of SaO2 detected at the ear by an oximeter. This measure reflects the circulatory delay due to cardiac dysfunction. DISCUSSION HCM is the most common hereditary cardiac disease and is characterized by left ventricular hypertrophy that may lead to diastolic heart failure. The annual rate of sudden cardiac death, the most feared complication of HCM, ranges from 0.5% to 1.5% per year for most age groups.1 We have recently reported a high prevalence of obstructive sleep apnea in 80 consecutive patients with HCM.2 Obstructive sleep apnea was independently associated with heart remodeling and atrial fibrillation in this population. In patients with systolic heart failure, CSR is an independent marker of poor prognosis3 and may be part of a vicious cycle, further stressing the failing heart in patients with congestive heart failure. CSR is characterized by a prolonged waxing and waning pattern of breathing interposed by central apneas. CSR has been extensively described among patients with systolic congestive heart failure with low ejection fraction. The prevalence of CSR among patients with systolic congestive heart failure is strikingly high and ranges from 30% to 50%.3 One of the key features of CSR is hyperventilation and low arterial PaCO2 that, when it falls below the apnea threshold during sleep, triggers central apneas.4 Patients with CSR present a low PaCO2 both awake and asleep. Our patient also presented a low awake PaCO2 (33 mmHg). The mechanisms leading to