Hemodynamic Changes Induced by Recreational Scuba Diving: Cardiac Function Assessment

Examinations were made using 2D and M-mode echocardiography associated with pulsed and continuous-wave Doppler. Echocardiography allows the measurements of cardiac diameters and LV systolic function; Doppler permits the measurements of CO as well as an assessment of LV filling pattern.
Images were obtained via a transthoracic approach from the parasternal views (long axis and short axis) and from an apical four-chamber view. The subjects were placed in a left lateral position for the parasternal views and in a supine position for the apical four-chamber view. Second harmonic imaging was used to improve the image quality. Doppler recordings were performed at the end of normal expiration in order to eliminate the effects of respiration on the parameters studied. Measurements were averaged from at least three consecutive beats. Tape recordings were obtained at a paper speed of 100 mm/s with simultaneous tracing of the ECG. Examinations were recorded on standard videotape for later review.

Cardiac Size and LV Systolic Function: Left atrial (LA) diameter, LV end-systolic diameter (LVESD), LV end-diastolic diameter (LVEDD), LV end-systolic and end-diastolic interventricular septal thickness, and LV end-systolic and end-diastolic posterior wall thickness were measured by M-mode echocardiography from the left short- and long-axis views. LV mass (LVM) was assessed by M-mode echocardiography and the application of the Devereux formula: LVM = 1.04 X ([LVEDD + LV end-diastolic interventricular septal thickness + LV end-diastolic posterior wall thickness] — LVEDD) — 13.6. Standard index of global LV systolic performance was LV percentage of fractional shortening (%FS). %FS was taken as the ratio of (LVEDD – LVESD)/LVEDD.
Determination of CO Across the Aortic Valve: CO was derived from aortic blood flow. Aortic cross-section diameter was measured by 2D echocardiography from the left parasternal short-axis view at the level of the aortic root. The aortic cross-section area (ACSA) was calculated as follows: ACSA = 3.14 X (diameter/2)2. The aortic systolic flow velocity time integral (VTI) was measured by computer-assisted determination using the pulsed-wave Doppler profile of aortic blood flow from the apical four-chamber view allowing to calculate LV SV [LV SV = aortic systolic flow VTI X ACSA] and CO (LV CO = LV SV X HR).

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