Valvular Heart Disease
MITRAL STENOSIS: Characterized by incomplete opening of the mitral valve during diastole, which limits antegrade flow and yields a sustained diastolic pressure gradient between the LA and LV.
Etiology
Rheumatic fever is the predominant cause of MS. 2/3 are females, common assoc. with MR, fish-mouth orifice of stenotic valve.
Other causes: SLE, RA, mitral valve annulus calcification, oversewn or tight mitral annulopasty ring. mitral valve prosthesis dysfunction or "patient-prosthesis" mismatch.
Functional MS may occur with obstruction of left atrial outflow due to tumor, particularly myxoma, LA thrombus, endocarditis with large vegetation, congenital membrane of the LA.
Pathophysiology
▼ MVA > diastolic pressure gradient develops between LA and LV
Gradient severity depends on:
Tranvalvular flow rate (~CO)
Diastolic filling time (~HR)
Valve obstruction (~ valve area)
▲ LAP > LA enlargement occurs in an attempt to compensate to attempt lower LAP
▲ LAP, LAE, and LA remodelling > AF > LA thrombus
▲ LAP is transmitted to pulmonary venous system > DOE / pulmonary edema / ▲ pulmonary vascular resistance/pumonary HTN > RV pressure overload > RVH > RV dilates and fails > CO decreases due to significant obstruction to flow from pulmonary vascular resistance and MS with exercise initially, then at rest > fatigue/DOE/decreased functional capacity.
Clinical features
History: DOE, orthopnea, PND, fatigue, palpitations (AF), systemic embolism, hemoptysis, CP, and/or signs of infective endocarditis.
Physical Exam depends on severity and time for adaptation of compensatory responses, include:
▲S1 (flexible valve leaflets)
OS - sudden tensing of valve leaflets with closing of the stenotic leaflets of mitral valve. A2-OS interval (shorter the interval more severe the stenosis).
The murmur will increase in intensity with leg raising, squatting, and expiration.
Mid-diastolic rumble - low pitched murmur, heard best at the apex with the bell of stethoscope. Severity of stenosis is related to the length of duration of murmur.
Loud P2, TR murmur, PA tap, and/or RV heave
▲JVP, hepatic congestion, and peripheral edema.
Dxtic:
ECG: P mitrale (P wave duration in lead II >0.12 or more, indicates LAE), AF, RVH
CXR: LAE, enlarged RA/RV and/or enlarged pulmonary arteries, calcification of the MV and/or annulus. The left heart border appears straightened and there is elevation of the left mainstem bronchus.
TTE: Assess etiology of MS, valvular and subvalvular apparatus to determine if patient is a candidate for percutaneous mitral balloon valvulotomy (PMBV), mitral valve area, mean transmitral gradient, PASP, RV size and function
TEE: clot, severity of MR. MV morphology and hemodynamics when TTE is suboptimal.
Exercise test with echo: Clarify functional capacity in those with an unclear history. Assess transmitral valve gradient and PA pressure with exercise when there is a discrepancy between resting Doppler findings, clinical findings, signs, and symptoms.
Left hearth cath: is the most accurate test. Used to determine severity of MS, when echo and clinical assessment are confusing. To determine cause of pulmonary HTN if it is out of proportion to the severity of MS. Also used to assess the reversibility of pulmonary HTN.
Severe MS
Mean gradient > 10 mm Hg
PASP > 50 mm Hg
Valve area (cm2) < 1
Tx:
Medical: Aimed at slowing progression of pulmonary HTN, prevention of endocarditis, reducing risk of VTE, and reducing HF sx.
HF: intermittent diuretics and low salt diet
Sx only with exercise: Likely associated with tachycardia, give BB, or non-dihydropyridine CCBs.
Antibiotic prophylaxis against rheumatic fever, since most MS is rheumatic in origin.
AF: Prone to AF and AFL - 30% - 40% of cases of MS
Exacerbation and worsening of symptoms, due RVR leading to shortening of diastolic filling period and due to loss of atrial kick.
Rate control and prevent thromboembolism (anticoagulation)
BB, verapamil, diltiazem are better than digoxin (slow response)
ACC/AHA Guidelines - Class I indications for anticoagulation for prevention os systemic embolization in patients with MS:
MS + AF
MS and prior embolic event, even if patient is now in NSR
MS with left atrial thrombus
Maintain NSR (DCCV, ablation, pharmacological). Challenging prospect.
PMBV
ACC/AHA Guidelines - Class I Indications for PMBV
Sx (NYHA class II, III, or IV) with moderate or severe MS and valve morphology favorable for PMBV in the absence of LV thrombus or moderate to sever mitral regurgitation.
Contraindications: LA thrombus, moderate to severe MR, an echo score of >8 (reflects thickening, mobility, and calcification of the leaflets and subvalvular apparatus; a relative contraindication)
Complications: death (~1%), stroke, cardiac perforation, severe MR needing surgical correction, and residual ASD requiring closure).
When done right in patients with favorable MV morphology, event-free survival (no immediate like death, repeat valvotomy, or MV replacement) is 80% - 90% at 3 - 7 years.
Surgical
ACC/AHA Guidelines - Class I Indications for Surgery for Mitral Stenosis
Symptomatic patients with NYHA class III or IV with moderate or severe MS in a patient with acceptable operative risk when:
PMBV not available
PMBV is contraindicated
Sx patients with moderate or severe MS who have moderate to severe MR should receive valve replacement, unless repair is possible at time of surgery.
On cardiac bypass - open
Not on cardiac bypass - close
Outcome and prognosis: MS progresses slowly, long latent period (decades) between rheumatic fever and the development of stenosis causing symptoms.
Asx or minimal sx Pts have an 80% 10-year survival
Severe sx: 0 - 15% 10- year survival.
Once pulmonary HTN develops the mean survival is 3 years.
Mortality in order of frequency for untreated patients: progressive pulmonary and systemic congestion, systemic embolism, pulmonary embolism, and infection.
AORTIC STENOSIS: is the most common cause of obstruction of flow from the LV to aorta - it is present in 2% of those >65 years of age and 4% of those >85 years of age.
Etiology:
Supravalvular
Subvalvular
Both fixed (subaortic membrane)
Dynamic: HCM with obstruciton (HOCM)
Aortic sclerosis is thickening of the aortic valve leaflets that cause turbulent flow through the valve without significant gradient. Over time it develops into AS.
Epidemiology:
Calcific/dengenerative
Most common cause in U.S
Trileaflet calcific AS usually seen in 7th - 9th decades
Risk factors same as CAD, worsened with abnormal calcium metabolism
Calcification leads to stenosis in both trileaflet and bicuspid valves.
Bicuspid
1% - 2% of population (congenital lesion)
Usually seen in 6th - 8th decades
~50% of patients who end up getting AVR for AS have a bicuspid valve
More prone to endocarditis than trileaflet valves
Associated with aortopathies (i.e., dissection, aneurysm) in a significant proportion of patients.
Rheumatic
More common worldwide, much less common in the United States
Seen in 3rd - 5th decades
Almost always accompanied by mitral valve disease.
Pathophysiology:
Aortic stenosis results from thickening, calcification, and/or fusion of the aortic valve leaflets, resulting in valvular obstruction. Impairment in opening of the cusps leads to pressure overload, compensatory left ventricular hypertrophy, and reduced ventricular compliance.
LVH to reduce wall stress (Laplace's law: Wall stress = pressure x radius/2 x thickness).
LVH maintains normal wall stress and a normal EF. If the increase in wall thickness does not increase in proportion to the rise in intraventricular pressure, wall stress will increase and EF will fall. It is important to assess whether a reduced EF is the result of excessive afterload (i.e. inadequate hypertrophy to overcome the obstruction) or depressed contractility. If the latter is present, surgical risk is higher.
In patients with excessive LVH, wall stress is low and the heart will become hyperdynamic with a very high EF. This finding portends a worse prognosis after surgical correction.
Angina may result from the increased oxygen demand caused by increased myocardial demand caused by increased wall stress, from reduction in blood supply per gram of hypertrophied tissue, and/or limited coronary vasodilator reserve. Thus, it may occur with or without concomitant CAD. Symptoms of CHF result from elevation of filling pressures due to diastolic dysfunction and eventually by progressive decline in LV systolic function. CO is fixed across the valve orifice and can lead to syncope in the face of peripheral vasodilatation.
The development of AF commonly causes symptoms due to the dependence of the hypertrophied ventricle on atrial "kick" to maintain a satisfactory stroke volume.
The degree of AS is determined by measuring the CO and peak or mean pressure gradient across the valve (pressures obtained from the left ventricle and aorta). A valve area is calculated from the ration of the cardiac output to the square root of the valve gradient (the Gorlin formula).
AVA = CO / (SEP x HR) / 44.5 x root of mean gradient. (SEP = systolic ejection period per beat)
AVA (normal = 2.5 - 3.5 cm2)
Dx:
History: Classic triad of sx included angina, syncope, and HF.
Physical Exam:
Harsh crescendo-decrescendo murmur heard best in Aortic area and radiating to carotids; time to peak intensity correlates with severity (later peak ~ more severe).
Diminished or absent A2 (soft S2) suggest severe AS.
An OS suggest bicuspid AS.
S4 reflects aortic contraction on a poorly compliant ventricle.
Pulsus parvus et tardus: late peaking and diminished carotid upstroke in severe AS.
Gallavardin phenomenon in an AS murmur heard best at the apex (easily confused with MR)
Dxtic testing:
ECG: LAE and LVH
CXR: LVH, cardiomegaly, and calcification of the aortia, aortic valve, and/or coronaries.
TTE: calculate valve area using continuity equation and measure transvalvular mean and peak gradients.
Severe AS:
Peak jet velocity in m/s > 4
Mean transvalvular gradient in mm Hg > 40
Valve area in cm2 < 1
AS may be graded as mild (AVA >1.5 cm2), moderate (AVA = 1 - 1.5 cm2), severe (AVA <1 cm2), or critical AVA (<0.75 cm2). More precisely, the valve area should be indexed to the patient's size, since a valve area of 1 cm2 may not be significant in a small patient but may be very significant in a larger patient. Critical AS is present when the AVA index is less than 0.45 cm2.
TEE
Bicuspid valve status if unclear on TTE.
To check other causes of LVOT obstruction
Excercise testing: Done if sx not clear. BP < 20 mm Hg on exercise and symptomatic.
Dobutamine stress echo: Used to assess LV dysfx with a small calculated valve area suggestive of severe AS, however the mean transvalvular gradient < 30 - 40 mm Hg.
Cath
Patients undergoing AVR who are at risk of CAD
AS with anginal sx
Gorlin formula
CTA may be an alternative to evaluated coronary anatomy prior to valve surgery
BNP or NtBNP (N terminal pro-B-type natriuretic peptide)
Treatment
Severe symptomatic AS needs surgery.
HTN: treat cautiously to avoid hypotension. ACEI is good choice.
Statins shown to slow progression of AS
Avoid diuresis as loss of preload can precipitate hypotension.
Severe AS with decompensated HF
IABP (contraindicated in patients with moderate to severe AR) - ▼ SVR
Sodium nitroprusside - ▼ SVR
Balloon aortic valvuloplasty
Afterload reduction facilitates forward flow and transient end-organ damage is reversed
Percutaneous transcatheter aortic valve replacement via transfemoral or transapical approach.
Surgical: ACC/AHA Guidelines - Class I Indications for AVR
Symptomatic patients with severe AS
Patients with severe AS (< 1 cm2)undergoing CABG
Patients with severe AS undergoing surgery on the aorta or other heart valves
Patients with severe AS and LV systolic dysfunction (EF <50%)
Outcome and Prognosis: Once patients experience symptoms, their average survival is 2 - 3 years with a high risk of SCD.
TRICUSPID STENOSIS
Tricuspid stenosis is very rare
Tricuspid regurgitation is seen 2° to mitral valve disease > pulm. htn > RV dilatation > tricuspid annular dilatation.
RV systolic dysfx results in elevated RA pressures, systemic venous pressures > Right sided HF. AF is common. Forward output is reduced leading to sx fatigue.
TR may develop as a result of endocarditis, usually in association with IVDA.
Indications for surgery:
Repair of TR is indicated for class III-IV sx, including hepatic congestion, ascites, and peripheral edema that is refractory to salt restriction and diuretics.
Repair of TR is indicated for severe symptoms or when moderate to severe functional TR is present at the time of left-sided valve surgery.
Severe TR with mean PA pressure <60 mm Hg and the patient is symptomatic after a trial of diuretics.
Surgery is high risk if the mean PA pressure exceeds 60 mm Hg, especially in the absence of left-side valvular disease.
Persistent sepsis or recurrent pulmonary embolization from tricuspid valve vegetations is an indication for surgery.
Preoperative considerations:
Passive congestion of the liver frequently leads to coagulation abnormalities which should be treated aggressively before and during surgery
Salt restriction, digoxin, and diuretics may improve hepatic function
Maintenance of an elevated CVP is essential to achieve satisfactory forward flow.
Sinus rhythm provides better hemodynamics than AF.
Slower HR are preferable for TS and faster HR preferable for TR.
Due to the necessity of placing sutures near the conduction system, patients are more prone to developing heart blocks after tricuspid valve surgery.
MITRAL REGURGITATION
Causes: HTN, IHD, and other conditions that lead to dilation of heart → separation of mitral valve leaflets.
Clinical features: DOE is the most common complaint.
Holosystolic murmur, heard best at the apex and radiates to the left axilla.
Murmur ▲ in intensity on leg raising, squatting, and hand grip.
Murmur ▼ in intensity on standing, Valsalva, and amyl nitrate inhalation.
S3 gallop.
Tx:
Acute: IV nitroprusside, IAPB while waiting surgery - aggressive afterload reduction. CO is HR dependent, don't slow HR by giving BB.
Chronic: nothing
Functional MR: ACEI/ARBs,furosemide
Surgical Management
ACC/AHA Guidelines - Class I indications for Surgery in MR:
Acute symptomatic MR in which repair is likely.
Pt. with NYHA functional class II, III, or IV symptoms with normal LV function defined as ejection fraction of 0.60 (60%) and end-systolic dimension of >45 mm
Symptomatic or asymptomatic patients with mild LV dysfx, EF 0.5 - 0.6, and end-systolic dimension 45 - 50 mm.
Symptomatic or asymptomatic patients with moderate LV dysfx, EF 0.3 - 0.5 and/or end-systolic dimension 50 - 55 mm.
MV repair is recommended over MV replacement in the majority of patients with severe chronic MR who require surgery, and patients should be referred to surgical centers of experience in MV repair.
Preoperative factors that increase operative and/or postoperative mortality inlcude: worse NYHA fuctional class, LV dysfunction (EF <60%), age, associated CAD, and AF.
AORTIC REGURGITATION
Pathophsiology: AR results from abnormalities in the aortic valve leaflets (postinflammatory deformity, bicuspid valve, destruction from endocarditis) or from aortic root dilatation that prevents leaflet coaptation (annuloaortic ectasia, aortic dissection with cusp prolapse). Acute AR from endocarditis or type A dissection produces acute LV failure and pulmonary edema because the ventricle is unable to dilate acutely to handle the volume overload. The sudden large regurgitant blood volume is imposed on LV which may be of normal or small size, with normal or decreased compliance. There is rapid increase in LVEDP and LAP. In order to maintain adequate CO the HR increases, and the contractility of LV increases. As attempts to maintain forward SV/CO may be inadequate, pulmonary edema occurs. Concurrent myocardial ischemia resulting form decreased coronary perfusion pressure and increased myocardial oxygen demand, lead to shock.
Chronic AR produces pressure and volume overload of the left ventricle, resulting in progressive LV dilatation, increase in wall stress, progressive hypertrophy (eccenteric and concentric), and symptoms of left-sided failure. The compensatory mechanisms maintain a relatively low LVEDP, adequate forward SV/CO, and sufficient coronary perfusion pressure. Eventually, increased afterload due to regurgitant volume load, leads to further ventricular dilatation, leading to increased wall stress > inability to continue further LVH > impaired contractility > fall in EF/SV/CO, and increased LVEDP. Angina due to decrease in coronary perfusion pressure and CHF symptoms occur.
Etiology
Common: Bicuspid aortic valve, rheumatic disease, calcific degeneration, infective endocarditis, idiopathic dilatation of the aorta, myxomatous degeneration, systemic HTN, dissection of the aorta, Marfan's syndrome.
Less common: Traumatic injury to aortic valve, collagen vascular diseases (ankylosing spondylitis, rheumatoid arthritis, Reiter's syndrome, giant cell aortitis, and Whipple's disease), syphilitic aortitis, discrete subaortic stenosis, VSD with prolapse of an aortic cusp.
Acute: IE, dissection of the ascending aorta, trauma
Treatment
Role of medical therapy is limited.
LV dysfx needs surgery.
Vasodilator therapy with ACE-I, hydralazine, to control systemic HTN. However, excessive afterload reduction may reduce diastolic coronary perfusion pressure and exacerbate ischemia.
Indications for surgery: ACC/AHA Guidelines - Class I indciations for AVR.
Symptomatic with severe AR irrespective of LV systolic function.
Actue AR with CHF
Endocarditis with hemodynamic compromise, persistent bacteremia or sepsis, conduction abnormalities, recurrent systemic embolization from vegetation, or annular abscess formation.
Symptomatic patients with severe AR. If EF >50%, surgery is recommended for patients with NYHA functional class III - IV. If EF <50%, surgery is also recommended for patients with NYHA functional class II.
Surgery is recommended in patients with:
EF < 50%
EF > 50% but evidence of progressive LV dilatation (end-diastolic dimension > 75 mm or end-systolic dimension > 55 mm at rest) or decline in EF > 5 % with exercise.
For patients with bicuspid aortic valve, Marfan's syndrome or related genetically triggered aortopathy, surgery on the aorta should occur at the time of AVR if the aortic root or ascending aorta is >4.5 cm.
NO IABP