Population

We consecutively recruited 59 patients who presented to Ibn Rochd University Hospital with MS suitable for PTMC between April and March 2009. All patients provided informed consent. Of these, there were seven men, with mean age of 31.0 ± 8.3 years. Eight had atrial fibrillation, and four had histories of prior PTMC. None had systemic hypertension, diabetes mellitus, more than mild mitral or aortic regurgitation and/or aortic stenosis, New York Heart Association functional class > III, or previous aortic or mitral valve surgery. Indications for PTMC were New York Heart Association class II or III, planimetered mitral valve area < 1.5 cm ² , mitral regurgitation ≤ 2+, suitable valve morphology, and absence of concomitant cardiovascular disease requiring surgical correction. Ten age-matched healthy women with a mean age of 30 years (range, 23–38 years), were also examined to determine normal RV Tei index and IVA. Measurement of dP/dt was not possible in all of these volunteers; although most of them had some degree of mild tricuspid regurgitation, their jet velocity profiles were not sufficiently clear to not allow consistently accurate measurement at the time in early systole when velocity had increased to 2.0 m/sec.

Echocardiographic Measurements

Two-dimensional echocardiography and Doppler studies were performed before and 24 to 48 hours after PTMC. All studies were obtained using a Vivid 7 ultrasound imaging system (GE Healthcare, Milwaukee, WI) equipped with a 3.5-MHz transducer. All measurements were performed using the recommendations of the American Society of Echocardiography. Two-dimensional images of the mitral valve were obtained from the parasternal short-axis view, and planimetry of the mitral orifice area was performed from these images (two-dimensional planimetry) just before PTMC. The peak and mean mitral valve transvalvular pressure gradients and late filling velocities were measured using the Bernoulli principle from continuous-wave Doppler recordings through the center of mitral inflow. The Wilkins score was used to judge mitral leaflet mobility, valvar and subvalvar thickening, and calcification. Twenty-four to 48 hours after mitral balloon dilatation, mitral valve area was again determined by planimetry. Systolic pulmonary artery pressure (SPAP) was derived from the tricuspid regurgitant jet peak velocity using the modified Bernoulli equation (peak gradient = 4 V ² , where V is the maximal velocity of the tricuspid regurgitant jet using continuous-wave Doppler). We further assumed a right atrial mean pressure of 10 mm Hg in patients, on the basis of the absence of inferior vena cava dilation > 20 mm. Tricuspid regurgitation was assessed qualitatively using semiquantitative guidelines and graded as follows: none, grade I (within 1 cm of valve), grade II (regurgitant jet area/right atrial area < 19%), grade III (regurgitant jet area/right atrial area, 20%–40%), and grade IV (regurgitant jet area/right atrial area > 40%).

The Tei index of RV myocardial performance was calculated as the time between tricuspid valve closure to tricuspid valve opening, divided by the RV ejection time, determined by pulsed Doppler. Doppler-derived dP/dt was determined as follows: the two points on the tricuspid regurgitation spectrum corresponding to 1 and 2 m/sec were identified. These points corresponded to RV–right atrial pressure gradients of 4 and 16 mm Hg using the modified Bernoulli equation ( P = 4 V ² ). Doppler-derived dP/dt was defined as dP/dt = 16 − 4/dt = 12 mm Hg/dt; dP/dt was determined from the initial portion of the tricuspid regurgitation spectrum, using the time required for velocity to increase from 1 to 2 m/sec as a measure of dt.

Pulsed-wave Doppler tissue imaging was performed by activating the machine’s Doppler tissue imaging function, with gain adjusted to eliminate transvalvular flow velocities and minimize noise. A 3.5-mm sample volume was placed on the lateral side of the tricuspid annulus. Peak myocardial velocities during systole, early, and late diastole together with the isovolumic contraction time were measured at a sweep speed of 100 mm/sec. IVA was measured by dividing myocardial velocity during isovolumic contraction by the time interval from onset of the myocardial velocity during isovolumic contraction to the time at peak velocity of this wave. The final values of all parameters were obtained after averaging over three cardiac cycles.

PTMC

All patients underwent PTMC by the antegrade transseptal approach using an Inoue balloon and a stepwise dilatation strategy. The nominal balloon diameter was decided according to the height of the patient (height [cm]/10 + 10 = balloon diameter]. Echocardiography was done at the end of the procedure to assess for perforation and to look for an atrial left-to-right shunt using color flow Doppler. Successful PTMC was defined as postvalvuloplasty valve area > 1.5 cm ² with no more than 2+ mitral regurgitation.

Statistical Analysis

Data are expressed as mean ± SD. Analysis used Student’s t tests for paired data to determine the significance of differences before and after PTMC.

To show the relationship between the variables in the patient groups, Pearson’s correlation analysis was performed. P values < .05 were considered statistically significant. SPSS version 16.0 (SPSS, Inc., Chicago, IL) was used.