title: Comparison of hemodynamic adaptation to orthostatic stress in patients with hypertrophic cardiomyopathy with or without syncope and in vasovagal syncope.
abstract: This study was designed to investigate whether, in patients with hypertrophic cardiomyopathy (HC), tilt-induced volume unloading triggers a peripheral reflex similar to that seen in patients with a history of vasovagal syncope or rather acts through an intrinsic cardiac mechanism secondary to diastolic dysfunction. Thirty-seven patients with HC (10 with and 27 without a history of syncope), 10 patients with vasovagal syncope, and 9 controls underwent 70 degrees head-up tilt for 45 minutes during continuous radionuclide monitoring of left ventricular function. We focused on the initial 5 minutes into the tilt test, well before symptoms occurred, to exclude that the observed hemodynamic changes were the consequence rather than the cause of syncope. HC patients with previous syncope and vasovagal patients experienced significant hypotension after the initial 5 minutes of tilt. Only HC patients with a history of syncope had a significant decrease in cardiac output, which began at the initial stage of the test. Systemic vascular resistance decreased in vasovagal patients, but increased in the HC syncopal group. Baseline peak filling rate was lower (2.4 +/- 0.5 vs 3.3 +/- 1.1 stroke counts/s, p = 0.03) and a "pseudonormal" or a restrictive pattern of left ventricular filling was more frequent (70% vs 26%, p = 0.02) in HC patients with than without a history of syncope. Thus, significant hypotension or frank syncope during orthostatic stress in HC patients with a history of syncope is due to an early decrease in cardiac output, which occurs well before the onset of symptoms; such impaired hemodynamic adaptation seems to be related to diastolic dysfunction.
authors.affiliation: Department of Clinical Medicine, Cardiovascular and Immunological Sciences, Federico II University School of Medicine, Naples, Italy.
authors.forename: Fiore
authors.initials: F
authors.lastname: Manganelli
authors.forename: Sandro
authors.initials: S
authors.lastname: Betocchi
authors.forename: Quirino
authors.initials: Q
authors.lastname: Ciampi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Storto
authors.forename: Maria Angela
authors.initials: MA
authors.lastname: Losi
authors.forename: Anna
authors.initials: A
authors.lastname: Violante
authors.forename: Carlo
authors.initials: C
authors.lastname: Briguori
authors.forename: Carlo Gabriele
authors.initials: CG
authors.lastname: Tocchetti
authors.forename: Raffaella
authors.initials: R
authors.lastname: Lombardi
authors.forename: Alberto
authors.initials: A
authors.lastname: Cuocolo
authors.forename: Massimo
authors.initials: M
authors.lastname: Chiariello
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D002302:Cardiac Output; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D004452:Echocardiography; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007022:Hypotension / Q000503:physiopathology; D008297:Male; D011877:Radionuclide Imaging; D013575:Syncope; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D018667:Tilt-Table Test; D014655:Vascular Resistance