61. Cardiac arrhythmias.

Cardiac arthythmias – disorders of rate, rhythm, co-ordination and consequences of heart contractions.

Classification:

1. Delt with automatism disorders:

   1. nomotopic – impulses generation like under normal conditions occurs in sinus-atrial node:

      1. sinus tachycardy – cardiac contractions rate increasing; R-R are shortened;

      2. sinus bradycardy - cardiac contractions rate decreasing; R-R is prolonged;

      3. sinus (respiratory) arrhythmia – tachypnoe in inspiration and bradypnoe in expiration; R-R are alternated;

   2. heterotopic – sinus-atrial node weakening syndrome – pace-maker of Ist order is not sinus node but other structures of heart conductive system:

      1. atrial slow rhythm – pace-maker is in left atrium, contractions rate is less than 70 beatings per 1 min;

      2. atrio-ventriular rhythm – pace-maker is superior part (rate is 70-60), intermediate (60-50) or inferior part (50-40) of atrio-ventricular node;

      3. idio-ventricular ventricular rhythm – Giss’ fascicle or its arms are pace-makers (contraction rate is less than 40 in 1 min).

2. Delt with excitability disturbances:

   1. Extrasystols – additional contractions of all heart or only ventricles; such contractions names are extrasystols:

      1. sinus – is appeared due to premature contractions of sinus-atrial node cells part; interval T-P is shortened;

      2. atrial – ectopic excitement locus is in atria different parts; P is decreased, 2-phased, negative; T-P is prolonged (incomplete compensatory pause);

      3. atrial-ventricular – at ectopic impulse occurrence in atrio-ventricular node; excitement wave is spread in 2 dimensions: in normal in ventricles and in retrograde (up from below) in atria; negative P can interfere with QRS; simultaneous atria and ventricles contractions also can take place;

      4. ventricular – is characterized by complete compensatory pause after premature contraction;

      5. allorhythmia – extrasystoles alternation with normal systolic cycles;

      6. bigeminy – if one normal cycle and one extrasystole is alternated;

      7. trigeminy – if 1 extrasystole is alternated with 2 normal cycles;

      8. quadrigeminy – if 1 extrasystole is observed after 3 normal cycles.

   2. Paroxysmal tachycardia – rapidly repeated extrasystols despite physiological rhythm; rate is 140-250 contractions per 1 min; fit duration is different:

a) atrial – is the mostly widely spread.

3. Connected with conductance disturbances:

   1. blockades – arrhythmias caused by retardation or complete stoppage of impulses conduction through conductive system; possible reason is conductive easy injury:

      1. intraatrial – at impulses distribution retardation through atrial conductive system; it is observed at mitral stenosis at left atrium dilation, more seldom at myocardial infarction, myocardites et al; P duration is increased more than 0,11 sec and P is decomposed (P-mitrale);

      2. atrio-ventricular – impulses conduction is disturbed from atria to ventricles:

• of I^st degree – is determined by impulses conduction retardation – interval P-Q is prolonged more than 0,20 sec;

• of 2^nd degree – periodically QRS-complexes disappearance due to impulses conductance progressive disorders from atria to ventricles; it is known as Samoilov-Venkebah’s periods – progressing interval P-Q increasing up to one of excitements (usually 8^th or 10^th) is not conducted; then P-Q is gradually restored and prolonged;

• of 3^rd degree – every second-third contraction is failed or on the contrary only they are conducted;

• complete atrial-ventricular blockade – atria and ventricles are contracted independently one from another, every one - in its own rhythm: atria with 70, ventricles – about 35 contractions per 1 min (idio-ventricular rhythm);

1. intraventricular:

• - one-fascicled blockades of Giss’ fascicle: of right arm – M-shaped dilated QRS more than 0,12 sec in V1-V2, seldom in III and aVF; of left arm – if such R is in V5-V6 (specialists must differentiate blockade of left anterior arm and left posterior arm);

• 2-fascisled blockades: of both rami of left arm; of right arm and left anterior ramus; of right arm and left posterior ramus;

• 3-fascicled: simultaneous blockade of all 3 rami of Giss’ fascicle at which complete a/v blockade is developed.

2) Impulses accelerated conductance – Wolf-Parkinson-Wite’s syndrom – premature ventricles contraction, P-Q size is decreased; reason – additional conductance ways (in mitral and tricuspidal rings – Paladino-Kent’s fascicle, between Giss’ fascicle superior part and ventricles – Mahaim’s fascicle, between atria and atrio-ventricular node inferior part or Giss’ fascicle – James’ fascicle).

4. Linked with excitability and conductance combined disorders:

1) Twinkled arrhythmia:

1. Atrial trembling (palpitation) – atria contraction rate is 250-400 per 1 min; main pathogenetic link is so-called re-entry mechanism when impulses are going round and round (often round cava veins and enter the heart; prognosis is more favourable comparatively to atrial fibrillation; EKG: frequent (250-350 in min) regular, similar atrial F-waves; non-changed ventricular QRS complexes (1 normal QRS after 2-3-4 F-waves).

2. Atria twinkling or fibrillation – impulses rate occuring in atria is 400-600 per 1 min; it is chaotic excitement without any order and atria muscular fibers separate groups contractions; such fibers are pathological impulsation origin; many ectopic focuses are generated in atrial myocardium; EKG: P-denses are absent; f-waves are registered in duration of all cardiac cycle; QRS complexes are not-changed but they are registered after different intervals (R-R are different); it is complication of such diseases as mitral stenosis, cardiosclerosis, thyreotoxicosis, myocardites, myocardial infarction; first fits are temporary, then they become constant;

1. Ventricles trembling – ventricles are contracted with rate equal to 150-300 per 1 min; sinusoid curve on EKG with frequent similar waves.

2. Ventricles twinkling (fibrillation) – impulses rate is 300-500 impulses in ventricles, heart is not contracted; none blood comes to aorta; different-shaped, with various altitude, chaotic and irregular waves, denses are not registered; electrical defibrillation should be applied.