Net atrioventricular compliance: A promising parameter in assesing rheumatic mitral stenosis

an LA compliance 
(Ca) can be obtained by dividing the cardiac stroke 
volume by the systolic rise in LA pressure. 
• The cardiac stroke volume can be calculated using 
the Fick method. 
• Similarly, mean left ventricular compliance (Cv) can 
be estimated as the stroke volume divided by the 
diastolic rise in left ventricular pressure. 
• Ventricular compliance can be calculated using a left 
ventricular catheter passed retrograde through the 
aortic valve. Fluid-filled catheters are used to 
measure the pressures. 
• Cn will then be calculated as (1/Ca+1/Cv) -1. 
Methods of measuring Cn 
Methods of measuring Cn 
• Cn can be readily calculated by Doppler 
echocardiography. 
• Cn was originally used for analysis of transmitral flow 
by Thomas and Weyman, demonstrating that the 
pressure halftime to estimate MV area varies 
inversely with orifice area but also directly with net 
left atrial and ventricular compliance and the square 
root of the peak transmitral gradient. 
Methods of measuring Cn 
• Flachskampf et al presented analytic and numeric 
evidence supporting the quantitative assessment of Cn 
from transmitral velocity profiles, deriving a simple 
equation that relates it to effective MV area and E-
wave downslope. 
• Schwammenthal et al showed that Cn can be 
calculated noninvasively and reproducibly in the clinical 
setting and correlates well with invasively determined 
values. 
Methods of measuring Cn 
• The net atrioventricular compliance is calculated by 
the formula. 
• Cn (mL/mm Hg)=1270×(planimetric MVA [cm2]/E-
wave downslope [cm/s2]). 
 E wave downslop implies E-wave dv/dt, where Cn - the net atrioventricular 
compliance, MVA -mitral valve area and E-wave dv/dt is the down slope of the 
mitral doppler signal in cm/sec2. 
 MVA s 1.7 sq cm, E wave down slope was 1.9 sq m. 
So his net atrioventricular compliance is 11.4 ml/mm Hg. 
• Background 
• Rheumatic mitral valvular heart disease 
• Concept of Compliance 
• Net atrioventricular compliance (Cn) 
• Methods of measuring Cn 
• Prognostic significance of Cn 
• Promising aspects of Cn in management of MS 
• Limitations of Cn as a parameter 
Outline 
Prognostic significance 
• Although Cn seemed to be an important determinant of cardiovascular 
performance in MS, few data were available on its prognostic 
implications. 
• The 1st study that evaluated the relation between Cn and clinical events 
was limited by the small number of patients enrolled and by an 
assumed cutoff value for Cn. The authors acknowledged the need for 
further prospective studies in more patients and the limitation of an 
assumed cutoff used for Cn in that analysis. 
 J Am Soc Echocardiogr. 2008;21:482–486. 
Maria Carmo P. Nunes et al (2013) showed that net 
atrioventricular compliance,Cn ≤4 mL/mm Hg best predicted 
unfavorable outcome in patients with mitral stenosis. 
Prognostic significance 
• In that study ,Cn was found adding prognostic 
information beyond that provided by clinical 
evaluation and MV area. 
Prognostic significance 
• Importantly, baseline Cn might provide its greatest 
value by predicting a progressive course with 
subsequent need for intervention in initially 
asymptomatic patients. 
• The authors concluded that Cn assessment therefore 
had potential value for clinical risk stratification and 
monitoring in MS patients. 
Intervention-free survival curves for patients stratified by net 
atrioventricular compliance (Cn) ≤4 
mL/mm Hg compared with patients with Cn >4 mL/mm Hg (log rank, 
30.5; P<0.001). 
Intervention-free survival curves for patients with moderate-to-severe 
anatomic mitral stenosis without indication for mitral valve intervention at 
baseline.The event-free survival rate was significantly higher in the 
patients with net atrioventricular compliance (Cn) >4 mL/mm Hg than in 
those with Cn ≤4 mL/mm Hg (log-rank, 15; P<0.001). 
Scatterplot showing correlation between systolic pulmonary artery 
pressure (SPAP) and net stiffness (1/net atrioventricular compliance 
[Cn]). There is a nonlinear negative relationship between Cn and SPAP 
and a positive correlation with stiffnes. 
Prognostic significance 
• In another study Maria Carmo P. Nunes et al (2013) showed 
that Cn is an independent predictor of death in patients with 
significant MS, even after adjustment for important 
prognostic factors. 
• The authors concluded that Cn reflected the overall 
hemodynamic consequence of the mitral valve obstruction, 
and should be considered in evaluating mortality risk in this 
setting. 
 JACC. March 12, 2013 Volume 61, Issue 10. 
• Background 
• Rheumatic mitral valvular heart disease 
• Concept of Compliance 
• Net atrioventricular compliance (Cn) 
• Methods of measuring Cn 
• Prognostic significance of Cn 
• Promising aspects of Cn in management of MS 
• Limitations of Cn as a parameter 
Outline 
Promising aspects of Cn in 
management of MS, where 
further researches are required 
• Detection of time of intervention: 
 Cn can predict the outcome of patients with MS, but still today 
the timing of intervention is dictated by patient’s symptoms, 
MVA, transvalvular pressure gradient, PASP etc. 
Promising aspects of Cn in 
management of MS. 
• Helping in choice of patient for intervention: 
 Where there is discrepancies between symptoms and 
conventional echocardiographic parameters, requiring more 
complete evaluation of physiology. 
 Baseline Cn may have its greatest use in this subset of patients 
by providing an additional indication of impaired physiology 
and progression to the need for intervention. 
Promising aspects of Cn in 
management of MS.. 
• Relation with impairment of RV function: 
• The pathophysiological mechanisms of RV dysfunction in MS are unclear. 
• RV dysfunction is not a simple expression of elevated pulmonary artery 
pressure. 
• Pande et al (2009) showed that RV dysfunction was observed in all cases 
of rheumatic MS regardless of PASP. 
• Sagie et al (1996) demonstrated that right heart disease can progress 
independently of MV area. 
• Maria Carmo P. Nunes et al (2013) showed that, echocardiographic indices 
of RV function weakly correlated with SPAP and had no independent effect 
on the clinical outcome. 
• In fact, normal RV function does not reliably exclude 
significant pulmonary hypertension in MS. 
• So a relation of decline Cn with RV function 
impairment in MS patient is not yet established and 
further studies are required to evaluate relation 
between RV function, PASP, Cn, MVA & transvalvular 
pressure gradient. 
Promising aspects of Cn in 
management of MS.. 
• Improvement of Cn following MV intervention is 
not yet established. 
 Aditya Kapoor et al (2004) found that left atrial compliance 
significantly improved immediately after successful balloon 
mitral valvotomy, irrespective of the pre valvotomy left atrial 
pressure. 
 The effect of a successful PTMC or MVR on Cn is still not 
evaluated. 
 If improvement occurs, whether this improvement is related 
to mortality or morbidity benefit is also not clear. 
Promising aspects of Cn in 
management of MS.. 
 An observational study titled “ Assessment of net 
atrioventricular compliance in patients undergoing 
PTMC” is going on in National Institute of 
Cardiovascular Diseases, Bangladesh. 
 We are expecting the result by the middle of next 
year. 
• Relation of Cn with patients age, disease duration & 
inflammatory markers is not yet determined. 
Promising aspects of Cn in 
management of MS.. 
• Background 
• Rheumatic mitral valvular heart disease 
• Concept of Compliance 
• Net atrioventricular compliance (Cn) 
• Methods of measuring Cn 
• Prognostic significance of Cn 
• Promising aspects of Cn in management of MS 
• Limitations of Cn as a parameter 
Outline 
Limitation of Cn as a 
parameter 
• Normal reference value is not available. 
• What’s the impact of age, sex, ethnicity & other 
demographic variable on Cn in not known. 
• The absolute value of Cn, to what extent it is 
significant is questionable. 
• Concomitant aortic valvular disease will causes 
underestimated Cn in MS by echocardiography. 
• Assessment of Cn in patients of MS who also have 
diastolic dysfunction will be misleading. 
• The invasive method of measuring Cn is not practical 
for routine use. 
• The echocardiographic method also requires good 
attention in determining E wave down slope as slight 
angulations may alter the Cn value. 
Limitation of Cn as a 
parameter 
Other potential aspects 
• Diastolic dysfunction of LV: 
Diastolic dysfunction of LV, with marked increase in 
filling pressure secondary to less compliant LV is now 
a well-known concept & is evaluated by different 
echocardiographic modalities. 
 LV diastolic dysfunction secondarily increases LA 
pressure & thus impairs LA compliance too. 
Diastolic dysfunction of LV 
 But in recently used echocardiographic modalities for 
diastolic function assessment the change in LA 
function is ignored. 
 Again a quantitative measurement of diastolic 
function is not available. 
 Cn may be a tool for assessing diastolic function of 
left heart & may provide a quantitative measure of 
diastolic function that will include LA disfunction. 
Conclusion 
• Cn is a promising parameter in Echocardiography. 
• It has increased our understanding of cardiac function in MS over 
conventional echocardiographic parameters. 
• There are numbers of issues where active researches are required 
to make it a fruitful variable in the management of MS. 
• We are hopeful that in the near future Cn will help the cardiologists 
to correlate demographic, clinical, anatomical & hemodynamic 
discrepancies in MS. 
• Cn also has the potential to be a valuable parameter in numbers of 
other cardiac conditions. 
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