Three common terms used to describe certain abnormal cardiac contractions are premature contractions (beats occurring early in time), ectopic beats (beats with sites of origin outside the sinus node), and extrasystoles (added beats). Only extrasystoles are truly added or additional beats, often interpolated or added between two normal beats without interfering with the basic rhythm.
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| Premature Contraction |
ATRIAL PREMATURE CONTRACTIONS
Premature atrial contractions are caused by an irritability of the atria, with early contractions emanating from an impulse in the atria outside the SA node. Atrial is differentiated from ventricular premature contractions by measurement of the compensatory pause. With atrial contractions the compensatory pause is incomplete, whereas with ventricular premature contractions the pause is complete.
Measurement of the compensatory pause for atrial premature beats follows: 1. Select the atrial premature beat (P wave) that appears different from the P waves of the basic mechanism and is premature in time; this is the atrial premature contraction. 2. Measure the interval from the premature P wave to the P wave immediately in front. 3. Add this measured interval to the time between the premature P wave and the P wave immediately following (<2×). This total duration is shorter than the time between two normal P-P intervals that do not include a premature contraction (2×).
NODAL PREMATURE CONTRACTIONS
Nodal premature contractions result from stimulation of the A-V node. Usually there is retrograde conduction starting at the A-V node, with an accession wave moving over the atria from the A-V node to the SA node, and P waves of an abnormal form are written. At times there is no retrograde conduction, and P waves and atrial contraction do not occur. The stimulus at the A-V node often is vagal or is caused by disease.
High Atrioventricular Nodal Rhythm
High A-V nodal rhythm prevails when the head of the A-V node becomes the pacemaker, and atrial depolarization occurs in a retrograde fashion from the A-V node to the SA node. With nodal premature contractions, inverted P waves are written in leads II, III, and aVF because of retrograde auricular depolarization. The P-R interval is short, P waves precede the QRS complexes, and the QRS and T waves are of normal configuration.
Middle Nodal Rhythm
When the junctional tissue is stimulated below the A-V node near its center, atrial and ventricular depolarizations occur simultaneously. Here the P waves fall within the QRS complexes, and the summation complexes (QRS + P) are slightly different in appearance from the normal QRS complexes of the basic mechanism.
Low Nodal Impulse
If the pacemaker is low in the junctional tissues, the ventricles are depolarized before the atria, the QRS complexes are written first, and inverted P waves in leads II, III, and aVF are written later.
RIGHT VENTRICULAR IMPULSE
The P wave rhythm is not disturbed. The ventricles contract early from a stimulus in the region of the right ventricle. The accession wave travels from right to left and, moving in this direction, produces upright QRS deflections in lead I. The duration of this complex is long because of the abnormally long pathway and is longer than 0.10 second, followed by S-T segments and T waves in the opposite direction as the major deflections of the QRS complexes. The compensatory pause is complete; that is, the interval between two normal QRS complexes that do not contain an ectopic beat is the same as the time from a QRS complex before the ectopic QRS beat to the QRS complex that follows this beat.
LEFT VENTRICULAR IMPULSE
A pacemaker in the LV wall produces an accession wave that travels from left to right, in lead I resulting in negative (inverted) wide QRS complexes with positive (upward) S-T segments and T waves and complete compensatory pauses.
References
1: Helmo FR, Alves EAR, Moreira RAA, Severino VO, Rocha LP, Monteiro MLGDR, Reis
MAD, Etchebehere RM, Machado JR, Corrêa RRM. Intrauterine infection, immune
system and premature birth. J Matern Fetal Neonatal Med. 2018
May;31(9):1227-1233. doi: 10.1080/14767058.2017.1311318. Epub 2017 Apr 20. PMID:
28423971.
2: Younger JD, Reitman E, Gallos G. Tocolysis: Present and future treatment
options. Semin Perinatol. 2017 Dec;41(8):493-504. doi:
10.1053/j.semperi.2017.08.008. PMID: 29191291.
3: Zhang L, Jiang Y, Wei M, Cheng BH, Zhou XC, Li J, Tian JH, Dong L, Hu RH.
[Analysis of the pregnancy outcomes in pregnant women with COVID-19 in Hubei
Province]. Zhonghua Fu Chan Ke Za Zhi. 2020 Mar 25;55(3):166-171. Chinese. doi:
10.3760/cma.j.cn112141-20200218-00111. PMID: 32145714.
4: Jacobsson B, Pettersson K, Modzelewska D, Abrahamsson T, Bergman L, Håkansson
S. Förtidsbörd största perinatala problemet - 5,7 procent av graviditeter i
Sverige slutar för tidigt, inte klarlagt varför – kostar miljardbelopp varje år
[Preterm delivery: an overview on epidemiology, pathophysiology and consequences
for the individual and the society]. Lakartidningen. 2019 Oct 8;116:FR6F.
Swedish. PMID: 31593284.
5: Leone Roberti Maggiore U, Ferrero S, Mangili G, Bergamini A, Inversetti A,
Giorgione V, Viganò P, Candiani M. A systematic review on endometriosis during
pregnancy: diagnosis, misdiagnosis, complications and outcomes. Hum Reprod
Update. 2016 Jan-Feb;22(1):70-103. doi: 10.1093/humupd/dmv045. Epub 2015 Oct 7.
PMID: 26450609.
6: Rasmussen SA, Smulian JC, Lednicky JA, Wen TS, Jamieson DJ. Coronavirus
Disease 2019 (COVID-19) and pregnancy: what obstetricians need to know. Am J
Obstet Gynecol. 2020 May;222(5):415-426. doi: 10.1016/j.ajog.2020.02.017. Epub
2020 Feb 24. PMID: 32105680; PMCID: PMC7093856.
7: Galindo-Sevilla N, Reyes-Arroyo F, Mancilla-Ramírez J. The role of complement
in preterm birth and prematurity. J Perinat Med. 2019 Oct 25;47(8):793-803. doi:
10.1515/jpm-2019-0175. PMID: 31494635.
8: Wahabi HA, Fayed AA, Esmaeil SA, Bahkali KH. Progestogen for treating
threatened miscarriage. Cochrane Database Syst Rev. 2018 Aug 6;8(8):CD005943.
doi: 10.1002/14651858.CD005943.pub5. PMID: 30081430; PMCID: PMC6513446.
9: Uberos J. The significance of genetics in pathophysiologic models of
premature birth. Minerva Pediatr. 2018 Aug;70(4):383-390. doi:
10.23736/S0026-4946.17.04994-5. Epub 2017 May 31. PMID: 28565902.
10: Pierce-Williams RAM, Burd J, Felder L, Khoury R, Bernstein PS, Avila K,
Penfield CA, Roman AS, DeBolt CA, Stone JL, Bianco A, Kern-Goldberger AR,
Hirshberg A, Srinivas SK, Jayakumaran JS, Brandt JS, Anastasio H, Birsner M,
O'Brien DS, Sedev HM, Dolin CD, Schnettler WT, Suhag A, Ahluwalia S, Navathe RS,
Khalifeh A, Anderson K, Berghella V. Clinical course of severe and critical
coronavirus disease 2019 in hospitalized pregnancies: a United States cohort
study. Am J Obstet Gynecol MFM. 2020 Aug;2(3):100134. doi:
10.1016/j.ajogmf.2020.100134. Epub 2020 May 8. PMID: 32391519; PMCID:
PMC7205698.
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