Cardiovascular disorders

II/2.7: Valvular heart diseases

II/2.7.1: Definition

Valvular heart diseases are valvular diseases where both morphologica and functional disorders are present in the same time.

II/2.7.2: Forms

Valvular heart diseases have two basic forms:

• - stenosis (that is, disorder of the opening function) and

• - insufficiency (that is, disorder of the closing function).

Both forms result in pathologic overload of the heart: stenosis causes hypertrophy by pressure overload, and insufficiency by volume overload. It follows that in stenosis, working muscle hypertrophy without dilation occurs (concentric left ventricular hypertrophy), and ventricular dilation, if there is any, is secondary, and indicates increasing exhaustion of the heart, while in insufficiency, ventricular dilation develops together with hypertrophy (eccentric left ventricular hypertrophy)

As long as the heart is able to compensate the increased load by its functional reserve, the valvular heart disease is called compensated, but as soon this reserve wears off, it becomes decompensated. Its clinical sign is the appearance of increasing circulatory failure symptoms.

During an autopsy it is easy to check the closing ability of primarily the aorta and truncus pulmonalis (valvular insufficiency test). In order to do this we hold the heart with its large arterial trunks upwards before we cut it, and fill both the aorta and truncus pulmonalis with water. In case of intact valves the level of the water doesn’t decrease in the large arterial stumps, but in valvular insufficiency the water streams down to the ventricle and it gradually disappears from the vessel. The examination of the semilunar valves (bicuspid or mitral valve and tricuspid valve) is more circumstantial, since we need to cut a hole on the apex of the ventricles and clamp the outflow tracts in the same time.

Then we hold the heart with its apex upwards, fill the ventricles with water, and observe the behaviour of the fluid level. The opening function (valvular stenosis test) can’t be checked with simple devices, it requires more elaborate pressure gauge (manometer) and flow-inducing (peristaltic pump) equipment which is beyond the capacity of a regular autopsy. Valvular stenosis is usually examined by observing and palpating the valves before cutting. However, detection of insufficiency by the above method may indirectly indicate valvular stenosis too, since the basic forms of valvular heart diseases don’t often go alone; and insufficiency usually is accompanied by stenosis and vice versa: stenosis is generally accompanied by insufficiency.

II/2.7.3: Mitral valvular heart diseases

In mitral insufficiency the left ventricle and atrium are dilated and moderately hyertrophic, and later, pulmonary congestion leads to right heart hypertrophy and exhaustion (cardiac failure). In mitral stenosis the left ventricle is underloaded and somewhat atrophic, the left atrium is significantly dilated and hypertrophic in some extent – due to limited baseline atrial muscular mass. In severe forms of mitral stenosis the former atrioventricular orifice narrows into a small gap, and this is called fishmouth-stenosis  (Knopflochstenose [button hole stenosis] in German) (macroscopic image No.8).

Macroscopic image No.8: Scarred fishmouth stenosis of the mitral valve. (From the archives of the 2nd Institute for Pathology, Semmelweis University – collected by Attila Kovács and István Kenessey).

II/2.7.4: Aortic valvular heart diseases

In aortic insufficiency eccentric left ventricular hypertrophy develops. A rare form of aortic valve insufficiency is fenestrated aortic valve. It is usually a small hole above the closing edge of the cuspid valves and thus it has no hemodynamic significance. However, in very rare cases the hole is bigger and it might extend even well below the closing line, and thus its hemodynamic significance gets greater. Due to backflow of blood (regurgitation) its effect is similar to that of a valvular insufficiency: it leads to left ventricular hypertrophy (macroscopic image No.9).

In infective endocarditis, destructive valvular rupture leads to sudden onset total valvular insufficiency; its instant consequence is cardiogenic shock, an acute catastrophe situation.

Macroscopic image No.9: Fenestrate aortic valve. The gap is much larger here than the average (also see macroscopic image No.1) and extends well below the cusps’ closing line. Its hemodynamic effect on the myocardium (valvular insufficiency) manifests in significant left ventricular hypertrophy. (From the collection of the 2nd Institute for Pathology, Semmelweis University – collected by Tibor Glasz).

In aortic stenosis concentric left ventricular hypertrophy develops first, and by gradually increasing decompansation it becomes eccentric. In exceptionally severe cases only a few mm fraction of the original aortic lumen remains patent (analogically with the mitral valve’s fishmouth stenosis). Pulmonary circulation gets congested and right heart failure develops in the end-stage. In hypertensive heart disease the lesions are substantially similar. Combined valvular heart disease  occurs in several cases, when degenerative valvular basis calcification (macroscopic image No.10) or free edge rigidity/calcification caused by rheumatic valvular disease leads to stenosis and insufficiency simultaneously, and the hardened valvular cusps are both narrowed and unable to close properly in the same time.

Macroscopic image No.10: Primary degenerative mitral valve calcification and secondary acute/subacute inflammation. Acute inflammation has caused valvular tissue damage. Degenerative valvular calcification is typically associated with annulus fibrosus calcification, and therefore it typically crawls up from the valvular basis to its cusps. Valves that were already affected are always more exposed to exacerbation (mainly superinfection) then a healthy valve. (From the archives of the 2nd Institute for Pathology, Semmelweis University – collected by Attila Kovács and István Kenessey).

II/2.7.5: Complications of valvular heart diseases

II/2.7.5.1: Chronic pulmonary heart

Secondary right ventricular overload, most frequently due to congestion in the pulmonary circulation caused by the sick left ventricle. More rarely it is caused by primary pulmonary disease (e.g. pulmonary fibrosis), pulmonary vascular disease, or pulmonary valvular heart disease. Morphologically there is right ventricular dilation and working muscle hypertrophy in the same time.

II/2.7.5.2: Relative valvular insufficiency 

It is almost always caused by severe ventricular dilation when the atrioventricular orifice’s surface grows in such a large extent that valvular cusps are unable to cover it completely. In exceptionally rare cases, mycotic (infective) aneurysm of a pulmonary artery and its thrombosis causes such pulmonary pressure increase that leads to the relative insufficiency of the pulmonary valve due to truncus pulmonalis circumference increase. In one of the preparations stored in the 2nd Institute for Pathology, Semmelweis University, this alteration is accompanied by ventricular septal defect, therefore left ventricular force has definitely contributed to the pressure increase in the pulmonary circulation and the dilating effect of luminal pressure exerted on the truncus pulmonalis.

However, in average cases the fibrous wall of arterial trunks gives such a massive frame to blood flow that no cardiac dilation can affect them, and they don’t dilate; and orifice dilations occur only in atrioventricular localisation.

II/2.7.5.3: Brown induration of lung

Chronic left heart failure leads to permanent congestion and relative hypoxia in the lung parenchyma. This leads to hemosiderin pigment deposition due to red blood cell infiltration into the interstitium, and fibroblast proliferation due to long-term hypoxia. These two processes together change the lungs’ color and consistency, their ’brown induration’. Histologically it manifests in heart failure cells and interstitial fibrosis.

II/2.7.5.4: Surgical therapy of valvular heart diseases

During valvuloplasty the surgeon keeps the original valve, and only corrects its shape. Replacement of the whole valve is neccessary in case of incorrigible morphological and structural disorders, and artificial valve is implanted in these cases. So-called mechanic valvular prostheses (macroscopic image No.11) are made of metal, and they are durable, last out over a lifetime, but mechanical red blood cell destruction occurs during each heartbeat at the snapping (closing) edges of their metallic parts, therefore it has a mild hemolytic effect in the long run. The patients need antithrombotic therapy throughout their life. So-called biological valves are lyophilized prostheses of animal (swine) origin. They don’t have hemolytic effect, and no antithrombotic therapy is needed. Their drawback is that lyophilized biological tissues degenerate in time (approx. ten years), and their sudden rupture might lead to acute cardiac failure.