{
  "abstract": "A woman in her 90s with a history of atrial tachycardia diagnosed 6 months earlier and treated with verapamil was brought to the emergency department with sudden onset of dyspnoea. On arrival, her blood pressure was 118/70 mm Hg, heart rate 120 bpm, respiratory rate (RR) 24/min and oxygen saturation 88% on room air. Pulse oximetry was recorded using a bedside finger probe (BSM-1763, Nihon Kohden, Tokyo, Japan), with waveform fidelity confirmed by stable signal acquisition and concordance with the palpated radial pulse and electrocardiographic rhythm. Its waveform showed beat-to-beat alternation in amplitude ( figure 1A). Palpation of the radial artery revealed alternating strong and weak pulses, suggesting pulsus alternans. No jugular venous distension or leg oedema was present, with mild wheezing. ECG demonstrated a regular narrow-QRS tachycardia with abnormal P-wave morphology distinct from sinus rhythm, preceding each QRS complex with a regular PP interval and an isoelectric baseline, consistent with atrial tachycardia. Transthoracic echocardiography revealed severe global systolic dysfunction with an ejection fraction (EF) of 17% (previously 60%) and alternating aortic flow velocity, reflecting pulsus alternans (figure 2A). Coronary angiography showed no significant stenosis. Acute left-sided heart failure due to atrial tachycardia, possibly exacerbated by verapamil-related myocardial depression, was considered.",
  "authors": [
    {
      "affiliations": [
        "Emergency and General Internal Medicine, Rakuwakai Marutamachi Hospital, Kyoto, Japan"
      ],
      "name": "Takuya Nishizawa"
    },
    {
      "affiliations": [
        "Emergency and General Internal Medicine, Rakuwakai Marutamachi Hospital, Kyoto, Japan"
      ],
      "name": "Takeshi Ueda"
    }
  ],
  "title": "Dynamic detection of pulsus alternans using pulse oximetry: rate-dependent and Valsalva-induced changes",
  "uid": "db4a20f8-97fe-54ca-9857-3e501ee35386"
}