title: Effect of obstruction on longitudinal left ventricular shortening in hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  We investigated the cause of the midsystolic drop (MSD) in left ventricular (LV) ejection velocities that are observed with hypertrophic cardiomyopathy (HCM) and severe obstruction.
  
  
  BACKGROUND
  Dynamic obstruction is an important determinant of symptoms and adverse outcome. The MSD in velocity and flow occurs in patients with gradients >60 mm Hg. The nadir velocity in the LV occurs simultaneously with peak gradient.
  
  
  METHODS
  We studied 36 patients with obstructive HCM and an MSD and compared them with 15 patients with HCM and no obstruction and with 25 age-matched normal control subjects. We measured LV ejection velocity proximal and distal to LV obstruction as well as tissue Doppler velocities and time intervals.
  
  
  RESULTS
  The duration of contraction of both the septum and lateral wall is shorter in obstructed patients with the MSD than in nonobstructed HCM patients: septal contraction 203 +/- 68 ms vs. 271 +/- 41 ms (p < 0.001). Parallel reduction in the length of shortening was noted: 1.2 +/- 0.6 cm vs. 1.9 +/- 0.4 cm (p < 0.001). The ejection velocity nadir follows the septal and lateral peak velocities by 100 ms and 60 ms, respectively. The velocity nadir occurs as both walls rapidly decelerate to their premature termination: septal deceleration 79 +/- 35 cm/s2 vs. 48 +/- 21 cm/s2 (p < 0.001). With medical abolition of obstruction the MSD disappears and the duration and length of contraction normalizes.
  
  
  CONCLUSIONS
  These data indicate that the MSD is caused by premature termination of LV segmental shortening and is a manifestation of systolic dysfunction.
authors: Division of Cardiology, St. Luke's-Roosevelt Hospital Center, Columbia University, College of Physicians and Surgeons, New York, New York 10019, USA.
authors: Ivan
authors: I
authors: Barac
authors: Shrikanth
authors: S
authors: Upadya
authors: Robert
authors: R
authors: Pilchik
authors: Glenda
authors: G
authors: Winson
authors: Michael
authors: M
authors: Passick
authors: Farooq A
authors: FA
authors: Chaudhry
authors: Mark V
authors: MV
authors: Sherrid
mesh_terms: D000328:Adult; D000368:Aged; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D018619:Echocardiography, Doppler, Pulsed; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011336:Probability; D011379:Prognosis; D012016:Reference Values; D018570:Risk Assessment; D012720:Severity of Illness Index; D013318:Stroke Volume; D013599:Systole / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014694:Ventricular Outflow Obstruction / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*