POSITION OF THE PROBLEM 1- Importance of the problem:Mitral stenosis MS is the situation that occurs when themitral commissures are sticked together inducing diastolic narrowing of the m
Trang 1POSITION OF THE PROBLEM 1- Importance of the problem:
Mitral stenosis (MS) is the situation that occurs when themitral commissures are sticked together inducing diastolic narrowing
of the mitral opening surface, impeding thus blood flow from the leftatrium (LA) into the left ventricle (LV), hence increasing left atrialpressure, and in the long term, increasing pulmonary capillarypressure due to swollen pulmonary veins, then increasing pulmonarypressure (PP), and pulmonary vascular resistance (PVR), leading toright ventricular overload, finally right ventricular failure.Percutaneous transmitral commissurotomy (PTMC) is an effectivemethod of non surgical enlargement of the mitral opening surface.World literature showed an important role of PVR in thepathophysiology of MS, that contributes to the assessment, follow-up
of treatment and prognosis, being the most sensitive indice ofassessment of the diseased pulmonary artery Some studies found thereversibility of PVR, but PVR might remain fixed though surgery orPTMC have been carried out, and the prognosis in those patients wasworse than in those with reversible PVR In the contrary, quite a fewnumber of patients have seen their PVR and pulmonary arterypressure (PAP) notably decreased after successful procedures,surgical or with PTMC
Cardiac catheterization was the only method of assessment ofPVR, but the procedure is invasive that could not be performed inany Health center, and repeated several times on the patient Since
1980, non invasive assessment of PVR with cardiac Dopplerultrasound has been carried out, but in Vietnam so far, such a method
Trang 2has not been studied, in patients with tight MS as well as the
follow-up of post PTMC
Our work: “Assessment of pulmonary resistance with cardiac Doppler ultrasound in patients with tight mitral stenosis pre and post PTMC” has been carried out with the following objectives:
1 To study the PVR in patients with tight MS with Dopplercardiography (with head to head comparison with the PVR as
in cardiac catheterization) and with a number of factors related
to PVR
2 To study changes of PVR post PTMC and a number ofinfluencing factors
2- Contributions of this thesis
This is the first scientific work ever with a systematic study ofPVR with Doppler cardiography in patients with tight MS treatedwith PTMC This is a simple procedure, easy to perform, andsusceptible to contribute to assessing post PTMC results in patientswith tight MS The results may broaden the use of Dopplercardiography in provincial polyclinics having their department ofCardiology
PRESENTATION OF THE THESIS The thesis comprises 115 pages in size A4, repartitioned in 4
chapters, dealing with 2 pages for Position of the problem, 30 pagesfor the Overview, 17 pages for the Material and Method, 32 pages forthe Study results, 32 pages for the Discussion, 1 page for theConclusions, and 1 page for the Recommendations
Trang 3
CHAPTER I
OVERVIEW
1.3 Pathophysiology of MS
Pathophysiological changes vary following the severity of MS:
1.3.1 Increased transmitral gradient
1.3.2 Decreased transmitral blood flow and decreased cardiac output
This decrease is mainly due to mechanical cause followingsevere MS, and not LV failure
1.3.3 Increased PVR and PP
LA pressure is usually not markedly increased with mild ormoderate MS The mean LA pressure (mLAP) is usually>10mmHg,sometimes 15-20 mmHg with tight MS When the mitral stenosis isimportant, the increased LAP wil be followed by increasedpulmonary veins and capillaries, and increased PAP (reactionarypulmonary hypertension, or post capillary pulmonary hypertension).The ever increase of PAP will induce retraction at the level ofpulmonary arterioles, a reaction to pulmonary hypertension, thusinduce increased PVR, and increased PP (this is now mixedpulmonary hypertension, both pre and post capillary) Pre capillarypulmonary hypertension is related to pulmonary arteriolar lesions, aconsequence of reactionary retraction of pulmonary arterioles to theincrease of LA and pulmonary pressures The prolonged retractionwill have deleterious consequences on the pulmonary arterioles andalveolar arterioles, leading to restructuring and fibrosis of thearteriolar walls, hence irreversible lesions at this level The finalresult is, a second barrage from pulmonary arterioles is formed in
Trang 4addition to the impeded LA-LV blood flow due to MS, that is called
“the second barrage” or “the second stenosis” Former belief was thatany intervention would exert little impact on the outcome of MS atthis stage, but clinical findings and a number of studies have shownimprovement with time following the procedures on MS
1.3.4 Changes in the stress test
Only severe MS present with major changes in the stress test
1.3.5 Changes in the LA
Prolonged increased LA pressure induces dilated LA,structural changes in the LA wall, that favours atrial fibrillation, andthe formation of thrombus, a cause of stystemic embolization
1.3.6 Changes in the RV
The RV increases contractions for ensuring necessary bloodsupply for the body when the pulmonary pressure and resistance areelevated, resulting in RV hypertrophy, RV dilatation, tricuspidregurgitation induced by dilatation of the tricuspid ring (TR)
1.3.7 Changes in the LV
Around 25-30% of patients present with slight decrease of LVfunction, probably due to long term decrease of blood flow into theLV
1.5 MS manifestations in the clinic and laboratory
1.5.1 Clinical manifestations: Dyspnea, cardiac asthma and acute
pulmonary edema, hemoptisis
1.5.2 Laboratory
1.5.2.1 EKG: Possible LA hypertrophy, righ axis deviation, RV
hypertrophy, atrial fibrillation is fairly common
Trang 51.5.2.2 Chest Xray: Prominent cardiac left border with presence of
4 arches, pulmonary vascular congestion, presence of esophagealcompression at inferior 1/3rd with barium ingestion
1.5.2.3 Cardiac Doppler ultrasound: A very important exploration.
a TM mode: In most cases of tight MS, the EF diastolic slope
is < 15mm/sec
b 2D mode : Allows direct assessment of mitral orifice,
commonly used as the result is close to the mitral anatomy
c Trans Esophageal Echography (TEE): Allows detect
intraatrial and intra appendage thrombus more easily, and favoursmore accurate assessment of valvular and subvalvular lesions
d Doppler ultrasound : Of particular importance in the
assessment of the severity of MS
- Assessment of mitral valve area with pressure half time (PHT).
- Assessment of the MS severity with transmitral pressure gradient.
e Ultrasound stress test
The test is indicated in case of symptoms present but tight MS
is not found with echo at rest, or symptoms absent but tight MS isfound with echo
- Asessment of valve and subvalvular anatomy in MS:
Wilkins score (Table 1.2)
For isolated MS, the optimal Wilkins score for indicatingPTMC is ≤ 8
The procedure should be discarded if Wilkins ≥ 11, for thepatient’s safety
1.6 Treatment for MS: Medical, surgical, and PTMC.
Trang 61.7 Methods of assessing PVR
1.7.1 Catheterization
PVR is calculated as follows:
PVR = (PAPm – LAPm)/Qp (Woods Units – WU)
PAPm:mean pressure of PA (mmHg), LAPm:mean pressure of
LA (mmHg),
Qp: pulmonary blood flow (l/min)
In case of no intracardiac shunt, Qp is considered equal tosystemic output
Two often used methods of assessment of cardiac output :Thermal dilution and Fick’s method
1.7.2 Cardiac Doppler ultrsound
A host of studies have been carried out for assessing PVR withcardiac Doppler ultrasound; in 2003, in the USA, Abbas AE et algave the following formula as the result of their study:
PVR = TRV / TVIrvot x 10 + 0.16
PVR: Pulmonary vascular resistance – in Woods units
TRV: Maximal velocity of tricuspid regurgitant jet – in m/secTVIrvot: integral of time velocity at the right venticularoutflow tract – in cm
The formula has been included into Harvey Feigenbaum’s
2005 teaching program of ultrasound, and has been used by severalauthors in the assessement, follow-up of results of treatment ofpulmonary hypertension, of capability to strain of MS patients, aswell as in patients with organ grafting
1.8 Relationship between PVR and involved parameters
In 1997, Kim et al found a correlation between PVR and mitralorifice surface (r = -0.54) and the level of dyspnea NYHA The
Trang 7authors did not find any correlation between PVR and age, gender,and pre PTMC of mitral valves regurgitation.
In 1999, Gamra et al found that in elderly patients, AF, highWilkins’scoring, are risk factors having negative impact on the return
to normal of PVR
CHAPTER 2 MATERIAL AND METHOD 2.1 Material
204 patients with tight MS have been PTMCed with Inoueballoon at Viet Nam Heart Institute (VNHI), and the control group of
116 normal adults with similar repartition in age range, and gender.Duration of study: 7/2006 – 8/2008
2.1.1 Selection criteria
- Tight MS (MVA < 1.5cm2) and symptoms present (NYHA ≥ II)
- Wilkins score ≤ 10.
- Absence of LA thrombus on transthoracic echo (in patients
on sinus rhythm) or TEE (in AF or high risk of having thrombus)
- Isolate tight MS or tight MS with mild Mitral regurgitation
(MR) or mild Aortic regurgitation (AR)
2.1.2 Exclusion criteria
- Heavily diseased mitral valve and sub- valvular tissue(heavily thickened valves, important calcification, seriousmorphological changes, quite shortened chordae tendinae…) withWilkins score >10
- LA thrombus
- Anamnesis of embolization within 3 months, even withoutecho findings
Trang 8- Concomitant respiratory diseases (bronchial asthma, COPD),Systemic diseases…and other diseases inducing pulmonaryhypertension.
- Concomitant Tricuspid stenosis
- Absence of TR or very mild TR not allowing themeasurement of regurgitant spectrum maximal velocity
- All cases with an indication for PTMC have been chosenafter consultation at VNHI
- Clinical examination and cardiac ultrasound re-checked 24hrsbefore PTMC
- All cases have been PTMCed with Inoue balloon at VNHIcathlab
- 34 patients with tight MS have been catheterized prior toPTMC
- Clinical and cardiac Doppler ultrasound rechecks: PostPTMC: 24 hours, 3 months, 6 months, 1 year
2.2.3 How to carry out cardiac Doppler ultrasound
- The examination has been carried out at VNHI echo lab.onALOKA 5000, 2 transducers: 2.5 and 5MHz, M, 2D, Doppler(pulsed, continuous, colour coded)
Trang 9Cardiac Doppler ultrasound parameters:
M mode: Parameters related to cardiac morphology and
function (ACC criteria)
2D mode: Assessment of the morphology of valves,
subvalvular area, valvular commissures
Assessment of MVA (left side of sternum, short axis)
Cardiac Doppler ultrasound:
MVA: PHT method
Pressure gradients: Max and Mean
Assessment of MR : 3 levels of severity
Assessment of TR : 3 levels of severity
Assessment of Pulmonary pressure (PP) based on 4 chamberaxis with continuous Doppler ultrasound transducer from the cardiacapex
PAPs = (TRV)2 + RAPs PAPs = pulmonary systolic pressure (mmHg)
RAPs = RA systolic pressure
TRV = Maximal velocity of TR spectrum (m/sec)
As RAPs is estimated 10mmHg, then PAPs = (TRV)2 + 10(mmHg)
Based on the pulmonary systolic pressure, we have 3 levels ofPulmonary hypertension (PH) (fig 2.6)
- PH as by measuring the maximal velocity of the TRspectrum (Fig 2.7)
- PH as by assessing the time integral velocity of blood flow
at the RVOT (TVIrvot): Location: left side of sternum, short axis,using pulsed Doppler
Assessment of PVR with cardiac Doppler ultrasound:
Using the Abbas Amr E : PVR = TRV/TVIrvot x 10 + 0.16
Trang 102.3 Data processing
a Medical statistical method using software SPSS 15.0
b The results are presented as the mean ± standard deviation
(for variants) or % (with logic variants)
c Paired t test used for comparing pre and post PTMC results
Statistical significance when p<0.05
d r is the correlation coefficient :
From 7/2006 to 8/2008, 320 individuals pertaining to similar
age range, and gender, and belonging to 2 groups: Patients’ group
comprising 204 patients with tight MS, being PTMCed at VNHI and
Control group with 116 healthy individuals.
3.1.1 Demographics of the Patients’ group (MS)
Table 3.8 Demographics of the tight MS group
(%)
Age (years) 39.44 ± 10.79 (15 – 76)
Past history of commissurotomy (Surg/PTMC) 34 (16.7%)
Trang 11The mean age in the MS group is 39.44 ± 10.79 (15 – 76 yrs),Females: 81%, 4.2 times of Males (Table 3.8).
3.1.1.2 Occupation: 53.4% are peasants.
3.1.1.3 Start of symptoms before admission (Table 3.11):
Only 4.5% are aware of the time when symptoms started
3.1.2 Clinical and laboratory features
3.1.2.1 Functional symptoms (Table 3.12) Most patients are at
NYHA II stage (51%)
3.1.2.2 Physical findings (Table 3.13) In almost all patients, S1 is
short and accentuated, rumbling diastolic murmur, S2 accentuatedand/or splitted, a sign rather common in tight MS
3.1.2.3 A-P Chest Xray
130 cases (63.7%) presented with accentuated hilum, dilated
2nd left arch
3.1.2.4 EKG
58.8% are in sinus rhythm, 58.3% have right axis deviation,and 53.4% Right Ventricular Hypertrophy (RVH)
3.1.2.5 Some common Doppler echocardiography features
Table 3.15 Doppler echocardiography in the MS group (n = 204)
Trang 123.3.1 Doppler echocardiography in both groups
Table 3.18 shows clear cut higher values of PVR in the MSgroup as compared to the control group
3.3.2 Factors involved in PVR elevation in the pre PTMC group
3.3.2.1 MVA (on 2D mode)
Moderate inverted linear correlation with r = - 0.41.
3.3.2.5 NYHA level (Table 3.24): PVR in group NYHA II is lower
than in group NYHA III-IV, with statistical significance p< 0.05
3.3.2.6 Atrial Fibrillation (Table 3.25): PVR in AF group is strikingly higher in group with sinus rhythm p< 0.001.
3.3.2.8 Pulmonary systolic pressure
Strong linear correlation between PVR and pulmonary systolicpressure r = 0.69
3.4 Changes in clinical and Doppler echocardiography data right after PTMC
3.4.1 Changes in functional symptoms (Table 3.27): After PTMC,
patients with NYHA I increase to 29.9% while those with NYHA
IV decrease to only 1 patient (0.5%)
3.4.2 Changes in physical findings (Table 3.28): Net decrease in
hepatomegaly, tachycardia
3.4.3 Changes in Doppler echocardiography right after PTMC
3.4.3.1 Changes in MVA and hemodynamic parameters
Very early better changes of measured parameters in cardiacDoppler ultrasound right after PTMC (24 hours, particularly PVR)
3.4.3.2 Changes in MR (Table 3.30)