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Clinical introduction
A man in his 70s with a left bundle branch block and advanced valvular systolic heart failure (HF) presented with a subacute HF and low cardiac output (CO) (peripheral hypoperfusion, high lactic levels, symptomatic hypotension). Echocardiography confirmed severe reduction in left ventricular ejection fraction, global longitudinal strain and stroke volume, as assessed by outflow tract pulse Doppler. Acute HF therapy with dobutamine and levosimendan was started, leading to progressive haemodynamic improvement.
After suspension of inotropes, under conditions of haemodynamic stability, a cardiopulmonary ramp-protocol maximal exercise test (CPET) was performed, showing a peculiar breathing during the exercise (figure 1).
(A) VE pattern during a cardiopulmonary ramp-protocol maximal exercise test. In parallel, (B) VO2 and (C) PetO2–PetCO2 also present the same behaviour during the effort. MVV, maximal voluntary ventilation; PetCO2, end-tidal partial pressure of carbon dioxide; PetO2, end-tidal partial pressure of oxygen; VE, ventilation; VO2, oxygen intake.
Question
Based on these CPET findings, what is the most likely diagnosis?
Anxiety-based hyperventilation
Congenital central hypoventilation syndrome
Exercise periodic breathing
Oscillatory peripheral oxygen desaturation during effort
Answer: C
CPET showed an exercise-induced periodic breathing (PB) throughout the whole effort. Ventilation, oxygen intake, carbon dioxide (end-tidal partial pressure of carbon dioxide) and oxygen (end-tidal partial pressure of oxygen) tensions exhibit the same oscillatory behaviour (figure 1A–C).
In anxiety-based hyperventilation, breathing pattern is irregular but not cyclical, as in the case of congenital central hypoventilation syndrome, a paediatric disorder characterised by severe hypoventilation. Peripheral oxygen saturation is not shown on the image and it is usually also normal in PB.
During the hospitalisation a Cheyne-Stokes breathing with prolonged apnoea, followed by phases of hyperventilation, was noted and a polysomnography revealed severe sleep apnoea with 114 central apnoeas (figure 2A) and an Apnea–Hypopnea Index of 35.4 events/hour.
(A) Polysomnography revealed central sleep apnoeas. (B) Echocardiography confirmed severe left ventricle dilation with reduced systolic function. 3D-EDV, three-dimensional end-diastolic volume; EF, ejection fraction; GLS, global longitudinal strain; HR, heart rate; LVOT VTI, left ventricle outflow tract time velocity integral; SpO2, oxygen saturation; SV, stroke volume;
PB is a characteristic pattern of involuntary breathing consisting of cyclic waxing and waning of tidal volume,1 2 typical of advanced HF and marker of poor outcome, on top of other prognostic indicators.3 PB is attributed to many factors, including low CO (figure 2B), delaying the time required for the pulmonary venous blood to reach the central and peripheral chemoreceptors.2 Specifically, three factors play a pivotal role in exercise-induced PB: hyperventilation, low CO leading to increased circulatory delay and cerebrovascular reactivity to carbon dioxide. A PB reduction due to HF improvement was reported.4 In this patient disease-modifying drugs (low-dose beta blockers, sacubitril/valsartan, mineral receptor antagonist) were increased to the maximal tolerated dose and a cardiac resynchronisation device was implanted. At 2-year follow-up, the patient reported New York Heart Association class II with no further hospitalisations. Notably, a same ramp CPET showed PB persistence, suggesting how new HF therapies allow event-free survival even in the presence of PB, usually considered a poor short-term prognosis marker.
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Patient consent for publication
Footnotes
Twitter @MapelliMassimo
Contributors MM, ES and PA have all contributed substantially to this work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.