Fig. 37. c) complete third-degree A-V block
b) incomplete (first and second degree) block. The causes of a complete A-V block are:
— of organic character — myocardites, rheumatic cardites, stitching through conduction tracts in the course of operations;
— functional — in myocardial infarction toxins are formed having their influence on A-V node, but they are transitory;
— edema of tissues around conduction system as a result of inflammation (myocarditis), hyperkalemia, sharp elevation of n. vagus tone.
Here, clinically a rare pulse will be noted. In complete A-V nodal block independent P waves not connected with ventricular complex will be seen on the ECG. Ventricular complexes will be different as they originate from the excitation of various areas, and R-R intervals are identical. In this case sharp disorders of hemodynamics are observed. Morgagni-Adams-Stokes attacks (prolonged asystole on the ECG) are particularly grave, when, at some moment, a circulatory arrest occurs by the type of ineffective heart.
Hemodynamic shifts:
— bradycardia;
— increase of systolic volume;
— arterial hypertension with great pulse amplitude;
— increase of systolic pressure in the pulmonary artery and in the right half of the heart;
— increase of peripheral resistance and arteriovenous difference by oxygen. Clinical picture of asystole is presented in Table 12.
Table 12
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1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107 | 108 | 109 | 110 | 111 | 112 | 113 | 114 | 115 | 116 | 117 | 118 | 119 | 120 | 121 | 122 | 123 | 124 | 125 | 126 | 127 | 128 | 129 | 130 | 131 |
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