219:
230:
188:
196:
171:
greater as more of the "path" is "blocked" from its "end" point. Therefore, most of the important heart blocks are AV nodal blocks and infra-Hisian blocks. SA blocks are usually of lesser clinical significance, since in the event of SA block, the AV node contains a secondary pacemaker which would still maintain a heart rate of around 40 - 60 beats per minute, sufficient for
349:
in the resting state. However SA block is capable of causing problematic symptoms even so, and may also hint at conduction issues elsewhere in the heart, and therefore SA blocks are - despite their lower level of life-threatening risk - still "the most common indication for pacemaker implantation in
331:
SA and AV node blocks are each divided into three degrees, with second degree blocks being divided into two types (written either "type I or II" or "type 1 or 2"). In an SA block, the electrical impulse is delayed or blocked on the way to the atria, thus delaying atrial depolarization. By contrast,
170:
Clinically speaking, the blocks tend to have more serious potential the closer they are to the "end" of the electrical path (the muscles of the heart regulated by the heartbeat), and less serious effects the closer they are to the "start" (at the SA node), because the potential disruption becomes
94:
In severe cases where the heart's ability to control and trigger heartbeats may be completely ineffective or unreliable, heart block can usually be treated by inserting an artificial pacemaker, a medical device that provides correct electrical impulses to trigger heart beats, compensating for the
382:
The difference between SA node block and SA node suppression is that in SA node block an electrical impulse is generated by the SA node that doesn't make the atria contract. In SA node suppression, on the other hand, the SA node doesn't generate an electrical impulse because it is reset by the
344:
SA blocks rarely give severe symptoms, because even if an individual had complete block at this level of the conduction system (which is uncommon), the secondary pacemaker of the heart would be at the AV node, which would fire at 40 to 60 beats a minute, which is enough to retain
106:
in a living person; incorrect conduction or interference from external sources can lead to mild or serious symptoms depending upon the location of the blockage and how severely conduction is being blocked. Conduction is initiated by the
95:
natural pacemaker's unreliability. Therefore, heart block frequently has no effects, or mild and occasional effects, and is not life-threatening in the vast majority of cases, and is usually treatable in more serious cases.
629:
610:
332:
an AV block occurs in the AV node and delays ventricular depolarization. The term "Wenckebach block" is also used for some heart blocks, and can refer to a second degree type I block in
63:
Heart block should not be confused with other conditions, which may or may not be co-occurring, relating to the heart and/or other nearby organs that are or can be serious, including
159:"). SA and AV node blocks are each divided into three degrees, with second-degree blocks being divided into two types (written either "type I or II" or "type 1 or 2"). The term "
48:. Despite the severe-sounding name, heart block may cause no symptoms at all in some cases, or occasional missed heartbeats in other cases (which can cause light-headedness,
367:
In addition to the above blocks, the SA node can be suppressed by any other arrhythmia that reaches it. This includes retrograde conduction from the ventricles,
1363:
163:
block" is also used for second degree type 1 blocks of either the SA or AV node; in addition second-degree blocks type 1 and 2 are also sometimes known as "
297:
293:
462:
Of these types of infra-Hisian block, Mobitz II heart block is considered most important because of the possible progression to complete heart block.
521:
1004:
240:
Following the path of the electrical signals, the places where conduction can be blocked give rise to different kinds of heart blocks:
41:
694:
1421:
738:
575:
546:
1225:
1062:
404:
207:
504:
1416:
1230:
1220:
809:
417:
399:
1527:
1358:
972:
1398:
488:
1393:
412:
Type 2 second-degree AV block (Mobitz II), also known as a Hay block - due to a block in or below the bundle of His
1262:
1043:
444:
1338:
1333:
1257:
439:
60:, depending upon exactly where in the heart conduction is being impaired and how significantly it is affected.
1684:
1560:
1489:
1321:
1057:
115:("AV node") which also contains a secondary "pacemaker" that acts as a backup for the SA nodes, then to the
1679:
1472:
1455:
1388:
1308:
687:
57:
147:("Intra-Hisian" or "Infra-Hisian block" respectively). Infra-Hisian blocks may occur at the left or right
1777:
1522:
967:
218:
1504:
992:
977:
1051:
537:
Valentin Fuster; R. Wayne
Alexander; Robert A. O'Rourke; Robert Roberts; et al. (November 2000).
229:
1582:
1279:
1247:
1174:
901:
536:
451:
223:
160:
433:
Type 2 second degree heart block (Mobitz II) –a type of AV block due to a block within or below the
1706:
1532:
1462:
1252:
1149:
1130:
960:
733:
644:
456:
429:
Infra-Hisian block is that of the distal conduction system. Types of infra-Hisian block include:
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1215:
1037:
1019:
955:
822:
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703:
392:
279:
187:
127:. Blockages are therefore classified based on where the blockage occurs - namely the SA node ("
20:
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982:
897:
792:
273:
195:
112:
68:
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sitecoreprod.heart.org|beta.heart.org|www.heart.org|heart.org|*.azurewebsites.net|localhost
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1242:
1201:
827:
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633:
372:
311:
267:(often abbreviated "SA nodal block" or "SA block", sometimes written "Sinuatrial block")
152:
1696:
1494:
1316:
1267:
892:
839:
749:
88:
49:
638:
1756:
1607:
1565:
1480:
1298:
1196:
913:
856:
754:
655:
571:
542:
484:
259:
233:
76:
37:
1729:
1621:
1514:
1210:
264:
128:
45:
1751:
1143:
1124:
1111:
918:
797:
672:
649:
255:
164:
124:
108:
1744:
1652:
1550:
1542:
1440:
950:
943:
930:
660:
376:
368:
84:
1771:
1734:
1645:
780:
434:
346:
320:
306:
288:
172:
148:
144:
120:
116:
103:
72:
623:
619:
1666:
1640:
1484:
1432:
1105:
1081:
1028:
887:
199:
409:
Type 1 second-degree AV block (Mobitz I), also known as a
Wenckebach block
1601:
1499:
1289:
1188:
1014:
987:
938:
879:
80:
53:
602:
1629:
1179:
211:
203:
176:
336:, however the ECG features of the two are quite distinctly different.
155:") or the fascicles of the left bundle branch ("fascicular block" or "
541:(10th ed.). McGraw-Hill Professional Publishing. Figure 24–60b.
156:
79:
or other types of shock, different types of abnormal heart rhythms (
1555:
712:
136:
222:
Sinus rhythm (rate = 100/min) with 3:2 and 2:1 Type II AV block;
132:
1635:
1615:
770:
614:
64:
102:
uses electrical signals to maintain and initiate the regular
99:
33:
282:(often abbreviated "AV nodal block", "AV block" or AVB).
236:
with complete AV block and resulting junctional escape
40:. This is caused by an obstruction – a block – in the
111:("sinus node" or "SA node"), and then travels to the
592:
702:
562:
560:
558:
1769:
555:
479:Logan, Carolynn M.; Rice, M. Katherine (1987).
570:(32nd ed.). Elsevier. 2012. p. 227.
688:
483:. J. B. Lippincott and Company. p. 232.
481:Logan's Medical and Scientific Abbreviations
383:electrical impulse that enters the SA node.
1005:Arrhythmogenic right ventricular dysplasia
695:
681:
530:
67:(heart-related chest pain), heart attack (
56:), or may require the implantation of an
478:
42:electrical conduction system of the heart
568:Dorland's Illustrated Medical Dictionary
228:
217:
194:
186:
1770:
739:Spontaneous coronary artery dissection
676:
424:
1063:Nonbacterial thrombotic endocarditis
523:Electrophysiology: A Companion Guide
497:
258:(SA node or Sinus node), where the
13:
1359:Accelerated idioventricular rhythm
386:
353:Types of SA nodal blocks include:
339:
325:"Fascicular block" or hemiblocks.
14:
1789:
588:
334:either the SA node or the AV node
319:Within the fascicles of the left
123:to the point of the apex of the
179:in the majority of individuals.
36:'s rhythm due to a fault in the
1044:Subacute bacterial endocarditis
445:Left posterior fascicular block
391:There are three basic types of
515:
472:
440:Left anterior fascicular block
191:Conduction system of the heart
44:. Sometimes a disorder can be
1:
1561:Pulseless electrical activity
1490:Multifocal atrial tachycardia
1364:Catecholaminergic polymorphic
465:
357:SA node Wenckebach (Mobitz I)
214:periods; R-P/P-R reciprocity.
210:manifest in the form of 5:4
7:
10:
1794:
1505:Wandering atrial pacemaker
1052:non-infective endocarditis
993:Endocardial fibroelastosis
18:
1722:
1665:
1583:hexaxial reference system
1574:
1541:
1528:Jervell and Lange-Nielsen
1513:
1471:
1430:
1407:
1381:
1349:
1307:
1288:
1187:
1173:
1073:
1058:Libman–Sacks endocarditis
1027:
1013:
929:
878:
871:
808:
763:
720:
711:
596:
452:Right bundle branch block
305:Within the left or right
260:heart's signals originate
224:right bundle branch block
1463:Ventricular fibrillation
734:Coronary artery aneurysm
457:Left bundle branch block
182:
16:Disorder of heart rhythm
1740:Diastolic heart failure
1714:Athletic heart syndrome
1675:Ventricular hypertrophy
1409:Pre-excitation syndrome
1263:Left posterior fascicle
788:Acute coronary syndrome
728:Coronary artery disease
265:Sinoatrial nodal blocks
143:), and at or below the
32:) is a disorder in the
1258:Left anterior fascicle
1038:infective endocarditis
823:Hibernating myocardium
704:Cardiovascular disease
505:"Conduction Disorders"
420:(complete heart block)
405:Second-degree AV block
280:Atrioventricular block
237:
226:
215:
206:complicated by Type I
192:
21:Congenital heart block
1422:Wolff–Parkinson–White
1382:Premature contraction
1280:Adams–Stokes syndrome
983:Loeffler endocarditis
793:Myocardial infarction
418:Third-degree AV block
400:First-degree AV block
274:atrioventricular node
232:
221:
198:
190:
113:atrioventricular node
69:myocardial infarction
1589:Right axis deviation
1551:Sudden cardiac death
909:Pericardial effusion
852:Ventricular aneurysm
312:Bundle branch blocks
202:with acute inferior
58:artificial pacemaker
1594:Left axis deviation
1451:Atrial fibrillation
1446:Ventricular flutter
1369:Torsades de pointes
1243:Bundle branch block
1202:Sick sinus syndrome
988:Cardiac amyloidosis
973:Tachycardia-induced
828:Myocardial stunning
776:Prinzmetal's angina
745:Coronary thrombosis
373:atrial fibrillation
298:Infra-Hisian blocks
294:Intra-Hisian blocks
167:1" and "Mobitz 2".
153:bundle branch block
125:fascicular branches
1778:Cardiac arrhythmia
1697:Atrial enlargement
1495:Pacemaker syndrome
1417:Lown–Ganong–Levine
1339:Junctional ectopic
1334:AV nodal reentrant
840:Myocardial rupture
750:Coronary vasospasm
425:Infra-Hisian block
363:SA node exit block
238:
227:
216:
193:
89:respiratory arrest
1765:
1764:
1757:Obstructive shock
1661:
1660:
1608:Short QT syndrome
1575:Other / ungrouped
1566:Sinoatrial arrest
1481:Ectopic pacemaker
1377:
1376:
1197:Sinus bradycardia
1169:
1168:
1165:
1164:
914:Cardiac tamponade
867:
866:
857:Dressler syndrome
755:Myocardial bridge
670:
669:
577:978-1-4160-6257-8
548:978-0-07-135695-4
539:Hurst's The Heart
525:, Steinberg (ed.)
360:SA node Mobitz II
329:
328:
287:At and below the
234:Sinus tachycardia
119:and then via the
77:cardiogenic shock
38:natural pacemaker
1785:
1730:Cardiac fibrosis
1622:T wave alternans
1515:Long QT syndrome
1309:Supraventricular
1305:
1304:
1238:Intraventricular
1185:
1184:
1025:
1024:
876:
875:
721:Coronary disease
718:
717:
697:
690:
683:
674:
673:
594:
593:
582:
581:
564:
553:
552:
534:
528:
519:
513:
512:
501:
495:
494:
476:
243:
242:
129:Sinoatrial block
52:(fainting), and
1793:
1792:
1788:
1787:
1786:
1784:
1783:
1782:
1768:
1767:
1766:
1761:
1752:Rheumatic fever
1718:
1657:
1570:
1537:
1509:
1467:
1426:
1403:
1373:
1345:
1292:
1284:
1178:
1161:
1069:
1018:
1009:
925:
919:Hemopericardium
863:
804:
798:Unstable angina
771:Angina pectoris
764:Active ischemia
759:
707:
701:
671:
666:
665:
605:
591:
586:
585:
578:
566:
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556:
549:
535:
531:
520:
516:
503:
502:
498:
491:
477:
473:
468:
427:
389:
387:AV nodal blocks
342:
340:SA nodal blocks
307:bundle branches
256:sinoatrial node
185:
149:bundle branches
121:bundle branches
109:sinoatrial node
71:), any type of
23:
17:
12:
11:
5:
1791:
1781:
1780:
1763:
1762:
1760:
1759:
1754:
1749:
1748:
1747:
1745:Cardiac asthma
1742:
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1726:
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1653:Strain pattern
1650:
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1543:Cardiac arrest
1539:
1538:
1536:
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1525:
1523:Andersen–Tawil
1519:
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1511:
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1497:
1492:
1487:
1477:
1475:
1469:
1468:
1466:
1465:
1460:
1459:
1458:
1448:
1443:
1441:Atrial flutter
1437:
1435:
1428:
1427:
1425:
1424:
1419:
1413:
1411:
1405:
1404:
1402:
1401:
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1326:
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1324:
1313:
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1302:
1286:
1285:
1283:
1282:
1277:
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1275:
1270:
1265:
1260:
1255:
1250:
1240:
1235:
1234:
1233:
1228:
1223:
1213:
1204:
1199:
1193:
1191:
1182:
1171:
1170:
1167:
1166:
1163:
1162:
1160:
1159:
1158:
1157:
1152:
1140:
1139:
1138:
1133:
1121:
1120:
1119:
1114:
1102:
1101:
1100:
1095:
1090:
1077:
1075:
1071:
1070:
1068:
1067:
1066:
1065:
1060:
1048:
1047:
1046:
1033:
1031:
1022:
1011:
1010:
1008:
1007:
1002:
1001:
1000:
995:
990:
985:
980:
975:
970:
965:
964:
963:
951:Cardiomyopathy
948:
947:
946:
944:Chagas disease
935:
933:
927:
926:
924:
923:
922:
921:
916:
906:
905:
904:
895:
884:
882:
873:
869:
868:
865:
864:
862:
861:
860:
859:
854:
844:
843:
842:
832:
831:
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800:
795:
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685:
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664:
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601:
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597:Classification
590:
589:External links
587:
584:
583:
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454:
449:
448:
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426:
423:
422:
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415:
414:
413:
410:
402:
393:AV nodal block
388:
385:
377:atrial flutter
371:atrial beats,
365:
364:
361:
358:
341:
338:
327:
326:
323:
316:
315:
309:
302:
301:
300:respectively.
291:
284:
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269:
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251:
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247:
184:
181:
85:cardiac arrest
15:
9:
6:
4:
3:
2:
1790:
1779:
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1773:
1758:
1755:
1753:
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1746:
1743:
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1738:
1737:
1736:
1735:Heart failure
1733:
1731:
1728:
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1725:
1721:
1715:
1712:
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1705:
1703:
1700:
1699:
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1678:
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1654:
1651:
1647:
1646:ST depression
1644:
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1300:
1296:
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1281:
1278:
1274:
1273:Trifascicular
1271:
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1200:
1198:
1195:
1194:
1192:
1190:
1186:
1183:
1181:
1176:
1172:
1156:
1155:regurgitation
1153:
1151:
1148:
1147:
1146:
1145:
1141:
1137:
1136:regurgitation
1134:
1132:
1129:
1128:
1127:
1126:
1122:
1118:
1117:regurgitation
1115:
1113:
1110:
1109:
1108:
1107:
1103:
1099:
1098:regurgitation
1096:
1094:
1091:
1089:
1086:
1085:
1084:
1083:
1079:
1078:
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1072:
1064:
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941:
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936:
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928:
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829:
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813:
811:
807:
799:
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790:
789:
786:
782:
781:Stable angina
779:
777:
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769:
768:
766:
762:
756:
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751:
748:
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490:0-397-54589-4
486:
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435:bundle of His
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384:
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348:
347:consciousness
337:
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321:bundle branch
318:
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289:bundle of His
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173:consciousness
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142:
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117:bundle of His
114:
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96:
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73:heart failure
70:
66:
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59:
55:
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47:
43:
39:
35:
31:
27:
22:
1667:Cardiomegaly
1641:ST elevation
1628:
1614:
1600:
1581:
1485:Ectopic beat
1433:fibrillation
1268:Bifascicular
1206:
1142:
1123:
1104:
1080:
1050:
1036:
1029:Endocarditis
968:Hypertrophic
902:Constrictive
888:Pericarditis
846:
834:
817:
654:
643:
628:
609:
567:
538:
532:
522:
517:
508:
499:
480:
474:
461:
428:
390:
381:
366:
352:
343:
333:
330:
239:
200:Sinus rhythm
175:and much of
169:
140:
97:
93:
62:
54:palpitations
29:
25:
24:
1533:Romano–Ward
1500:Parasystole
1399:Ventricular
1351:Ventricular
1290:Tachycardia
1207:Heart block
1189:Bradycardia
1015:Endocardium
978:Restrictive
939:Myocarditis
880:Pericardium
272:Within the
254:Within the
81:arrhythmias
26:Heart block
1431:Flutter /
1394:Junctional
1329:Junctional
1322:Multifocal
1295:paroxysmal
1211:Sinoatrial
1180:arrhythmia
1175:Conduction
931:Myocardium
656:DiseasesDB
466:References
212:Wenckebach
204:infarction
177:daily life
161:Wenckebach
98:The human
19:See also:
1690:Pulmonary
1473:Pacemaker
1144:pulmonary
1125:tricuspid
961:Alcoholic
350:the US".
276:(AV node)
157:Hemiblock
104:heartbeat
46:inherited
1772:Category
1556:Asystole
1456:Familial
1150:stenosis
1131:stenosis
1112:stenosis
1093:stenosis
1088:prolapse
810:Sequelae
713:Ischemia
527:, p. 142
246:Location
208:AV block
137:AV block
956:Dilated
898:Chronic
706:(heart)
650:D006327
369:ectopic
133:AV node
50:syncope
1636:J wave
1389:Atrial
1317:Atrial
1106:aortic
1082:mitral
1074:Valves
1020:valves
872:Layers
741:(SCAD)
574:
545:
487:
375:, and
165:Mobitz
65:angina
1723:Other
1707:Right
1685:Right
1299:sinus
1248:Right
998:Viral
893:Acute
847:weeks
818:hours
730:(CAD)
661:10477
639:426.9
249:Name
183:Types
139:" or
100:heart
87:, or
34:heart
1702:Left
1680:Left
1297:and
1253:Left
835:days
645:MeSH
634:9-CM
572:ISBN
543:ISBN
485:ISBN
296:and
131:"),
630:ICD
624:I45
620:I44
611:ICD
141:AVB
83:),
1774::
1630:ST
1602:QT
1483:/
1231:3°
1226:2°
1221:1°
1216:AV
1209::
900:/
659::
648::
637::
618::
615:10
557:^
507:.
395::
379:.
314:.
151:("
135:("
91:.
75:,
30:HB
1616:T
1301:)
1293:(
1177:/
1017:/
696:e
689:t
682:v
632:-
622:-
613:-
603:D
580:.
551:.
511:.
493:.
28:(
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