Immediate Impact of Successful Percutaneous Mitral Valve Commissurotomy on Echocardiographic
Measures of Right Ventricular Contractility
Abdenasser Drighil, MD, Dounia Ghellab, MD, James W. Mathewson, MD, Loubna Ouarga, MD, Hanane Alalou, MD, and Laila Azzouzi, MD,Casablanca, Morocco; and Phoenix, Arizona
Background:Functional analysis of the right ventricle cannot be reliably evaluated by conventional echocar- diography, because of its complex geometry and load dependence of ejection phase indices. The Tei index, dP/dt, and myocardial acceleration during isovolumic contraction are parameters of right ventricular (RV) con- tractility unaffected by RV geometry. However, the effect of loading conditions on these parameters is contro- versial. The aim of this study was to examine how afterload reduction observed after percutaneous transverse mitral commissurotomy (PTMC) in patients with mitral stenosis affects these measures of RV contractility.
Methods:Fifty-eight patients (mean age, 30.068.3 years seven men, 52 women) with isolated rheumatic mitral stenosis, eight of whom had atrial fibrillation, were studied prospectively before and 24 to 48 hours after PTMC.
Results:Immediately after PTMC, mitral valve area increased from 1.060.2 to 1.860.3 cm2(P= .0001). There was a significant decrease in systolic pulmonary artery pressure from 50.2626.9 to 33.2612.3 mm Hg (P= .0001), a decrease in the RV Tei index from 0.560.2 to 0.360.2 (P= .0001), and an increase in RV dP/dt from 321.0659.9 to 494.66139.5 mm Hg/sec (P= .0001). RV myocardial acceleration during isovo- lumic contraction and systolic velocity at the lateral tricuspid annulus assessed by Doppler tissue imaging did not change. There were weak positive correlations among the Tei index, dP/dt, and systolic pulmonary artery pressure before PTMC (respectively,r= 0.39,r= 0.28, andP= .02,P= .05) but not afterward (respectively, r= 0.17,r= 0.02, andP= .20,P= .90).
Conclusions:This study suggests that RV dP/dt and Tei index are weakly load dependent, whereas myocardial acceleration during isovolumic contraction is unaffected by acute change in RV afterload. (J Am Soc Echocar- diogr 2012;25:1245-50.)
Keywords:Percutaneous mitral commissurotomy, Right ventricular contractility, Afterload, Mitral stenosis, Right ventricle, Myocardial acceleration during isovolumic contraction
Right ventricular (RV) functional assessment remains challenging in daily practice. Functional analysis of the right ventricle cannot be reliably evaluated by conventional echocardiographic techniques, be- cause of its complex geometry and load dependence of ejection phase indices.1The RV Tei index, dP/dt, and myocardial acceleration during isovolumic contraction (IVA), all indicators of RV myocardial contractility, are derived from Doppler and tissue Doppler measure- ments and are unaffected by RV geometry. However, the effect of loading conditions on these parameters is controversial.2The Tei in- dex and dP/dt are thought to be dependent on preloading condi-
tions,3-5 whereas IVA is thought to be preload independent. The impact of RV afterload changes on these parameters has not been rigorously examined to date. We performed this prospective study to determine how afterload reduction observed after percutaneous transvenous mitral commissurotomy (PTMC) in patients with mitral stenosis (MS) affects these measures of RV contractility.
METHODS
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 31.068.3 years. Eight had atrial fibrillation, and four had histories of prior PTMC. None had systemic hypertension, diabetes mellitus, more than mild mitral or aortic regur- gitation 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
From the Department of Cardiology, Ibn Rochd University Hospital, Casablanca, Morocco (A.D., D.G., L.O., H.A., L.A.); and St. Joseph Hospital and Medical Center, Phoenix, Arizona (J.W.M.).
Reprint requests: Abdenasser Drighil, Rue Epinale, Residence Espace Socrate E7, Socrate, Maarif, Casablanca, Morocco (E-mail:sdrighil@gmail.com).
0894-7317/$36.00
Copyright 2012 by the American Society of Echocardiography.
http://dx.doi.org/10.1016/j.echo.2012.08.010
1245
mitral valve area < 1.5 cm2, mi- tral regurgitation#2+, suitable valve morphology, and absence of concomitant cardiovascular disease requiring surgical correc- tion. Ten age-matched healthy women with a mean age of 30 years (range, 23–38 years), were also examined to deter- mine normal RV Tei index and IVA. Measurement of dP/dt was not possible in all of these volun- teers; 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 per- formed 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 measure- ments were performed using the recommendations of the American Society of Echocardiography.6 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 in- flow. The Wilkins score7was 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 deter- mined by planimetry. Systolic pulmonary artery pressure (SPAP) was derived from the tricuspid regurgitant jet peak velocity using the mod- ified Bernoulli equation (peak gradient = 4V2, whereVis 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.8Tricuspid 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%).9
The Tei index of RV myocardial performance was calculated as the time between tricuspid valve closure to tricuspid valve opening, di- vided by the RV ejection time, determined by pulsed Doppler.10 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 = 4V2). 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.11 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 mea- sured at a sweep speed of 100 mm/sec. IVA was measured by dividing myocardial velocity during isovolumic contraction by the time inter- val from onset of the myocardial velocity during isovolumic contrac- tion to the time at peak velocity of this wave.12The 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.13The nom- inal balloon diameter was decided according to the height of the pa- tient (height [cm]/10 + 10 = balloon diameter].14Echocardiography 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 cm2with no more than 2+ mitral regurgitation.
Statistical Analysis
Data are expressed as mean6SD. Analysis used Student’sttests 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.Pvalues < .05 were considered statistically significant. SPSS version 16.0 (SPSS, Inc., Chicago, IL) was used.
RESULTS
Eighty percent of patients (n = 47) were in New York Heart Association class II, and 20% (n = 12) were in class III before PTMC; by planimetry the mean mitral valve area was 1.0 6 0.2 cm2, and the mean SPAP was 50.26 26.9 mm Hg. Eighteen patients had SPAP > 50 mm Hg at rest, and four patients had SPAP
> 100 mm Hg.
PTMC was successfully completed in 58 patients. One patient who developed severe mitral regurgitation after PTMC and who required urgent mitral valve replacement was excluded from the study. There was no evidence of significant left-to-right atrial shunting. No patient had more than grade II tricuspid regurgitation either before or after PTMC. Comparisons of pre-PTMC and post-PTMC echocardio- graphic measurements and Doppler tissue imaging velocities are shown inTables 1and2, and one illustration from the same patient is shown inFigures 1 to 3.
After PTMC, the mean transmitral gradient decreased from 13.96 7.4 to 5.6 64.0 mm Hg (P< .0001), left ventricular end-diastolic diameter, left ventricular end-systolic diameter, and left ventricular ejection fraction remained unchanged.
The mean RV Tei index from 10 healthy adult volunteers was 0.260.1. The mean Tei index in patients with MS was 0.560.2.
The RV Tei index decreased significantly after PTMC (P< .0001;
Figure 1), and dP/dt increased significantly (P< .001).
There were correlations among Tei index, dP/dt, and SPAP before PTMC (respectively,r= 0.39,r= 0.28, andP= .02,P= .05) but not afterward (respectively,r= 0.17,r= 0.02, andP= .20,P= .90).
The mean IVA from 10 healthy adult volunteers was 4.061.5 m/sec2. The mean IVA in patients with MS was 3.361.2 m/sec2. IVA did not change significantly after PTMC. The systolic velocity (Sv) and isovolumic contraction velocity also did not change significantly.
Abbreviations IVA= Myocardial acceleration during isovolumic contraction MS= Mitral stenosis PTMC= Percutaneous transvenous mitral commissurotomy RV= Right ventricular SPAP= Systolic pulmonary artery pressure
Sv= Systolic velocity
DISCUSSION
In daily practice, cardiologists often find it difficult to manage patients with valvular heart disease who need valve replacement when they also have RV dysfunction. In effect, the postoperative outcome de- pends in part on RV function.15,16In the presence of RV failure, mortality increases perioperatively and during follow-up, and the per- sistence of symptoms after mitral valve surgery is higher in patients with preoperative RV dysfunction.15,16RV function depends on RV contractility and preload and afterload conditions. The influence of afterload changes on RV function is known (i.e., high SPAP and reduced RV function despite normal RV contractility), and generally RV systolic function improves after afterload decreases. In such cases, the prognosis is often good. However, in patients with depressed RV contractility, the improvement in preload and afterload conditions after surgery does not always improve the prognosis. In effect, Sadeet al.17showed that impaired RV contractile reserve portends high risk for a poor outcome. Hence, the use of load- independent measures of RV function is crucial for preoperative RV assessment and determining eventual prognosis.
In the present study, IVA did not change after PTMC despite fact that SPAP decreased significantly, suggesting that it is afterload inde-
pendent. Vogelet al.12previously showed that IVA is a measure of RV contractility unaffected by preload and afterload within physio- logic range. IVA has also been validated as a load-independent mea- sure of RV systolic function and is suggested to be a strong index of contractility, because it reflects the rate change of contractile force dur- ing isovolumic contraction.18Furthermore, Tayyareciet al.19showed that RV IVA may be used as a reliable adjunctive parameter for the early detection of RV systolic dysfunction in patients with MS before echocardiographic signs of systemic venous congestion. Also, Sade et al.17showed that IVA was the most important determinant of the he- modynamic severity of MS and that patients with preserved RV con- tractile reserve and high SPAP may still benefit from surgery and have favorable outcomes. They concluded that these patients may be better served by being identified before RV contractile dysfunction occurs.
Among other Doppler tissue imaging parameters, we found that tricuspid Sv also did not change after PTMC. Wanget al.20compared several echocardiographic variables with RV ejection fraction using cardiac magnetic resonance imaging and concluded that tricuspid Sv was the best independent predictor of RV ejection fraction. Sade et al.21showed that tricuspid Sv predicted RV ejection fraction if RV function was depressed and left ventricular function was preserved.
A strong correlation has been demonstrated between tricuspid Sv and RV fractional area change, regardless of the degree of pulmonary hypertension.22The absence of change of Sv before and after PTMC may be related to load independence, suggesting that it might serve as another measure of RV contractility, especially in the presence of pul- monary hypertension.
In the present study, RV dP/dt and RV Tei index improved signif- icantly after PTMC. This may mean an improvement of RV contrac- tile function but may also reflect the sensitivity of these parameters to afterload’s changes. This is suggested by the lack of correlation among dP/dt, Tei index, and SPAP before PTMC. We think this may be re- lated to the contribution of other factors to RV function, especially re- lated to the decrease in pulmonary arterial pressure. In a study by Menzelet al.23evaluating 24 patients with chronic thromboembolic pulmonary hypertension who underwent thromboendarterectomy, they found that the RV Tei index decreased significantly after throm- boendarterectomy (from 0.55 to 0.37,P< .05). However, they did not find a correlation between RV Tei index and mean pulmonary ar- tery pressure or pulmonary vascular resistance. In a similar study, Blanchardet al.24found, in 93 patients with chronic thromboembolic pulmonary hypertension, that Tei index decreased significantly after thromboendarterectomy (from 0.52 to 0.33, P < .0001).
Pulmonary vascular resistance was correlated with RV Tei index be- fore and after surgery (r = 0.78 and r = 0.67, respectively, P <
.0001), and the change in pulmonary vascular resistance was corre- lated with the change in RV Tei index (r = 0.75, P < .0001).
Interestingly, in this study, a significant decrease was noted in isovolu- metric times after surgery, but no significant change in RV ejection time, implying that with a reduction in afterload, RV dysfunction per- sists, which highlights the importance of load on RV performance. In our study, we used pulsed Doppler Tei index because it was our rou- tine practice. Doppler tissue imaging Tei index can also be used. Both pulsed Doppler Tei index and Doppler tissue imaging Tei index have shown to be accurate and give similar results.25
RV dP/dt is a contractility index that uses isovolumic contraction time and is a well-established and widely used measurements of left ventricular contractility. Few normal data are available for RV dP/dt because of its infrequent use in routine clinical practice and the ab- sence of tricuspid regurgitation in almost 83% of the healthy popula- tion.26 Although it has been suggested that RV dP/dt is less Table 1 Echocardiographic data before and immediately
after PTMC
Variable Before PTMC After PTMC P
LA anteroposterior diameter (mm)
4767 4268 .0001
MVA (mm2) (planimetry) 1.060.2 1.860.3 .0001 MVA (mm2) (PHT) 1.060.2 1.961.8 .0001 Mean transmitral gradient
(mm Hg)
13.867.4 5.564.0 .0001
LVEDD (mm) 4565 4765 NS (.07)
LVESD (mm) 2965 3065 NS
LVEF (%) 63.369.3 65.667.7 NS (.074)
RV diastolic diameter (mm) 23.263.9 21.763.3 .004 Tricuspid inflow
E tricuspid flow (cm/sec) 51.5613.2 53.2614.7 NS A tricuspid flow (cm/sec) 52.4619.1 49.3615.9 NS SPAP (mm Hg) 50.2626.9 33.2612.3 .0001 LA, Left atrial;LVEDD, LV end-diastolic diameter;LVEF, LV ejection fraction;LVESD, LV end-systolic diameter;MVA, mitral valve area;
PHT, pressure half-time;SPAP, systolic pulmonary artery pressure.
Data are expressed as mean6SD.
Table 2 Two-dimensional echocardiographic parameters of RV contractility before and immediately after PTMC
Variable Before PTMC After PTMC P
IVA (m/sec2) 3.361.2 3.261.2 NS
Isovolumic contraction velocity (cm/sec)
10.7610.3 10.362.8 NS
Sv (cm/sec) 12.062.6 12.062.6 NS
RV Tei index 0.560.2 0.360.2 .0001
dP/dt (mm Hg/sec) 321.0659.9 494.66139.5 .0001 Data are expressed as mean6SD.
dependent on afterload and more on preload,5our study suggests that this parameter is also afterload dependent.
Study Limitations
We did not use directly measured pulmonary artery pressures and car- diac output, even though we understand well the importance of cor-
roborating invasive data. Nevertheless, additional catheters and their associated procedure time prohibitively add to the cost of interven- tional procedures in the third world, where the need is great and facilities and resources are few. We justify their absence in our study because carefully performed, noninvasive methods for determining these and related hemodynamic parameters are now well established.
Figure 1 Example of patient’s RV isovolumic contraction (IVC) velocities, RV systolic (S) velocities, and RV IVA before (IVC veloc- ity = 16 cm/sec, S velocity = 13 cm/s, and IVA = 4.3 m/sec2) and after (IVC velocity = 17 cm/sec, S velocity = 14 cm/sec, and IVA = 4.5 m/sec2) PTMC. IVA was determined as the slope of a straight line from zero-line crossing to the peak of the IVC wave.
Figure 2 Example of time intervals of the myocardial performance index (Tei index) before PTMC (left; Tei index = 37%) and after PTMC (right; Tei index =23%). The RV Tei index was calculated by the difference ofa b/b, where theacomponent is measured from the trailing edge of late diastolic transtricuspid pulsed-wave Doppler (PWD) flow A wave to the leading edge of subsequent early diastolic transtricuspid PWD flow E wave, and thebcomponent is measured from the leading to the trailing edge of the RV outflow systolic PWD tracing.
CONCLUSIONS
Our study suggests that RV dP/dt and the RV Tei index are afterload dependent, while RV IVA and Sv are unaffected by an acute decrease in RV peak systolic pressure after PTMC. Furthermore, the RV IVA and Sv independence of ventricular geometry and straightforward measurement make these indices particularly attractive in evaluating patients with MS.
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