65. Cardiac insufficiency.

Cardiac insufficiency – is a pathological condition determined by heart non-ability to provide blood supply for organs and tissues according to their needs. It is a state when load to heart is higher than its ability to perform activity. It is expressed in following: heart can not transfer all blood to vascular bed coming to it through veins.

Types:

1) By clinical course:

1. acute;

2. chronic.

2) By clinical manifestations expression:

1. compensated (hidden);

2. b) visible (decompensated).

3) Dependently on primary dysfunction:

1. left-ventricular;

2. right-ventricular;

3. total.

4) By pathogenesis:

1. from overloading;

2. myocardial;

3. extramyocardial.

Cardiac failure from overloading is developed as a result of very big loads (with resistance or volume) action to healthy heart, id est when resistance to cardiac charge is increased or blood flow to heart separate chamber is rised up. Reasons: heart vices, large or small circulation circles hypertension, arterio-venous shunts or at very hard physical load performance. Excesive recquirements are given to the heart with normal contractive ability.

2 Overloads types:

1. Overload with volume – occurs when increased blood volume comes to heart or its separate chambers; heart or this chamber under overloading must transport increased blood volume in arterial system; t is reached by heart minute volume increasing correspondingly to increased venous return. There are 3 main cases:

   1. venous blood return increasing to heart – particularly at hypervolemy or veins hypertony (venous system capacity decereasing);

   2. heart vices- its valves insufficiency; left ventricle overloading is developed at aortal and mitral valves insufficiency; right ventricle – at pulmonary artery and tricuspid valve insufficiency.

2. Overload with resistance – occurs when heart or its separate parts have to perform work against increased resistance which prevents all blood transfer in arteries. Heart must save its minute volume despite increased resistance to blood exile. Cases:

   1. arterial pressure increasing (peripheral vascular resistance rising up); left ventricle has overload at large circle hypertension; right one – of small circle;

   2. heart vices – valvular foramens stenosis: at aorta foramen stenosis - left ventricle overload, mitral valve foramen – left atrium, pulmonary artery foramen stenosis – right ventricle, tricuspidal valve foramen - right atrium

Compensatory mechanisms at overloads action:

1. Urgent:

   1. heterometric mechanism;

   2. homeometric mechanism;

   3. chronoinothropic mechanism;

   4. catecholamines inotropic action.

2) Hypertyhrophy of myocardium - long-termed adaptation.

Heart and vessels work in complicated functional interrelations. Besides, heart has its own (myogenic) regulative mechanisms. One of them – heterometric – is performed as answer to myocardium fibres length change (Starling’s law). Such cardiac regulative mechanism can provide circulatory insufficiency compensation and its anomalies. It is characterized by very high sensitivity. It may be observed at introduction of 1-2 % of all circulating blood mass in magistral veins.

Second myogenic regulative mechanism type is homeometric. Myocardial fibres ending dyastolic stretching degree is not important for its realizing. The most important is correlation between cardiac contractions and aortal pressure (Anrep’s effect): aortal pressure increasing causes initial heart systolic volume decreasing and then – heart contractions force increasing and cardiac discharge stabilizing at new contractions level.

Thus, heart activity myogenic regulational mechanisms may permit its contraction significant changes.

Besides, heart has sympathetic and parasympathetic innervation like vessels. At tone dominance of one of them heart and vessels activity will be different.

Efferent nerves tone support is provided by cardiac-vascular regulation center. Heart-vascular regulative center – is a rather complicated structure in which dominant importance has its “working” part, located in medulla oblongata. It was there where neurons are located from which excitement are transmitted on effector ways (parasympathetic and sympathetic) while reaching heart and vessels. That’s why their reflectory regulation is always performed simultaneousely. When sympathetic nervous system tone is dominant (hypersympaticotony) than heart activity is increased:

• its contraction freaquency is rised up – positive chronotropic effect;

• contraction force is increased – positive inotropic effect;

• excitability is increased – positive bathmotropic effect;

• conductance is rised up - positive dromotropic effect.