title: Frequent premature ventricular contractions in an orbital spaceflight participant.
abstract: BACKGROUND
  Commercial spaceflight participants on orbital flights typically are older than career astronauts and they often have medical conditions that have not been studied at high g or in microgravity. This is a case report of a 56-yr-old orbital spaceflight participant with essential tremor and frequent premature ventricular contractions that occurred at rates up to 7000 per day. Before training and spaceflight, he was required to complete extensive clinical investigations to demonstrate normal cardiac structures and the absence of cardiac pathology. The evaluation included signal averaged ECG, transthoracic stress echocardiography, exercise tolerance tests, electrophysiological studies, cardiac MRI, electron beam CT, Holter monitoring, and overnight oximetry. While no cardiac pathology was demonstrated, the Russian medical team required that the PVCs be treated prior to training and spaceflight. For the initial flight, a selective beta-1 receptor beta blocker was used and for the second a calcium channel blocker was used in combination with a nonselective beta blocker for tremor control. Analogue environment testing assured that this combination of medications was compatible.
  
  
  CONCLUSIONS
  The spaceflight participant's PVCs were incompletely suppressed with a low-dose selective beta-1 blocker, but were well suppressed by a calcium channel blocker. He tolerated in-flight periodic use of a nonselective beta blocker in combination with a calcium channel blocker. In-flight ECG and blood pressure monitoring results were normal, and an ECG obtained midmission and on landing day showed successful PVC suppression. He did not have any cardiac difficulty with launch, on-orbit operations, entry, or recovery
authors.affiliation: Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, TX 77555-1110, USA. rjenning@utmb.edu
authors.forename: Richard T
authors.initials: RT
authors.lastname: Jennings
authors.forename: Jan P
authors.initials: JP
authors.lastname: Stepanek
authors.forename: Luis R
authors.initials: LR
authors.lastname: Scott
authors.forename: Yury I
authors.initials: YI
authors.lastname: Voronkov
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000337:Aerospace Medicine; D018480:Astronauts; D002121:Calcium Channel Blockers / Q000627:therapeutic use; D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory; D020329:Essential Tremor; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013026:Space Flight; D013997:Time Factors; D018879:Ventricular Premature Complexes / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D014893:Weightlessness / Q000009:adverse effects*
chemical_list: D000319:Adrenergic beta-Antagonists; D002121:Calcium Channel Blockers