関: QRS complex、QRS間隔

QRSの正常と異常

wide QRS, narrow QRS

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the 17th letter of the Roman alphabet (同)q

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(チェスの)queen

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/08/02 20:15:34」(JST)

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For other uses of the term "S wave", see S-wave.

Schematic representation of normal ECG

Diagram showing how the polarity of the QRS complex in leads I, II, and III can be used to estimate the heart's electrical axis in the frontal plane.

The QRS complex is a name for the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the right and left ventricles of the human heart. In adults, it normally lasts 0.06 - 0.10 s; in children and during physical activity, it may be shorter.

Typically an ECG has five deflections, arbitrarily named "P" to "T" waves. The Q, R, and S waves occur in rapid succession, do not all appear in all leads, and reflect a single event, and thus are usually considered together. A Q wave is any downward deflection after the P wave. An R wave follows as an upward deflection, and the S wave is any downward deflection after the R wave. The T wave follows the S wave, and in some cases an additional U wave follows the T wave.

Etiology

The His/Purkinje specialized muscle cells coordinate the depolarization of both ventricles, and if they are working efficiently the QRS complex is 80 to 120 ms in duration (represented by three small squares or less at the standard paper speed of 25mm/s). Any abnormality of conduction takes longer and causes "widened" QRS complexes. In bundle branch block there can be an abnormal second upward deflection within the QRS complex, and in this case the second upward deflection is referred to as R' (pronounced "R prime"). This would be described as an RSR' pattern.

Ventricles contain more muscle mass than the atria; therefore the QRS complex is considerably larger than the P wave. The QRS complex is often used to determine the axis of the electrocardiogram (although it is also possible to determine a separate P wave axis).

The duration, amplitude, and morphology of the QRS complex are useful in diagnosing cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte derangements, and other disease states.

Parameters

Schematic representation of the QRS complex.

Parameter	Normal value	Value comments	Clinical significance
QRS duration	0.06 - 0.10 sec^[1]	Shorter in children and in tachycardia^[2]	Prolonged duration indicates e.g. hyperkalemia.^[3] or bundle branch block
QRS amplitude	S amplitude in V1 + R amplitude in V5 < 3.5 millivolt (mV)^[2] R+S in a precordial lead < 4.5 mV^[2] R in V5 or V6 < 2.6 mV		Increased amplitude indicates cardiac hypertrophy
Ventricular activation time (VAT)	< 0.05sec in V5 or V6^[2] < 0.03sec in V1^[2]		Measured in increased QRS amplitude^[2]
Q wave	Duration more than 0.04 secs in leads other than III and AVR^[4] Amplitude less than 1/3 QRS amplitude^[4] (R+S) Amplitude less than 1/4 of R wave^[4]		Abnormality indicates presence of infarction^[4]

The QRS complex is also included in estimating the QT interval.

Q wave

Normal Q waves, when present, represent depolarization of the interventricular septum. For this reason, they are referred to as septal Q waves and can be appreciated in the lateral leads I, aVL, V5 and V6.

R wave progression

Looking at the precordial leads, the r wave usually progresses from showing a rS-type complex in V₁ with an increasing R and a decreasing S wave when moving towards the left side. There is usually an qR-type of complex in V₅ and V₆ with the R-wave amplitude usually taller in V₅ than in V₆. It is normal to have a narrow QS and rSr' patterns in V₁, and so is also the case for qRs and R patterns in V₅ and V₆. The transition zone is where the QRS complex changes from predominately negative to predominately positive (R/S ratio becoming >1), and this usually occurs at V₃ or V₄. It is normal to have the transition zone at V₂ (called "early transition"), and at V₅ (called "delayed transition").^[5]

The definition of poor R wave progression (PRWP) varies in the literature, but a common one is when the R wave is less than 2–4 mm in leads V₃ or V₄ and/or there is presence of a reversed R wave progression, which is defined as R in V₄ < R in V₃ or R in V₃ < R in V₂ or R in V₂ < R in V₁, or any combination of these.^[5] Poor R wave progression is commonly attributed to anterior myocardial infarction, but it may also be caused by left bundle branch block, Wolff–Parkinson–White syndrome, right and left ventricular hypertrophy as well as by faulty ECG recording technique.^[5]

J-point

The point at which the QRS complex meets the ST segment is known as the J-point. The J-point is easy to identify when the ST segment is horizontal and forms a sharp angle with the last part of the QRS complex. However, when the ST segment is sloped or the QRS complex is wide, the two features do not form a sharp angle and the location of the J-point is less clear. There is no consensus on the precise location of the J-point in these circumstances.^[6] Two possible definitions are:

The "first point of inflection of the upstroke of the S wave"^[6]
The point at which the ECG trace becomes more horizontal than vertical.^[7]

Monomorphic or polymorphic

Monomorphic refers to all QRS waves in a single lead being similar in shape. Polymorphic means that the QRS change from complex to complex.^[8] These terms are used in the description of ventricular tachycardia.

Terminology

Various QRS complexes with nomenclature.

Not every QRS complex contains a Q wave, an R wave, and an S wave. By convention, any combination of these waves can be referred to as a QRS complex. However, correct interpretation of difficult ECGs requires exact labeling of the various waves. Some authors use lowercase and capital letters, depending on the relative size of each wave. For example, an Rs complex would be positively deflected, while an rS complex would be negatively deflected. If both complexes were labeled RS, it would be impossible to appreciate this distinction without viewing the actual ECG.

References

^ III. Characteristics of the Normal ECG Frank G. Yanowitz, MD. Professor of Medicine. University of Utah School of Medicine. Retrieved on April 14, 2010
^ ^a ^b ^c ^d ^e ^f Compendium for interpretation of ECG at Uppsala Institution for Clinical Physiology. Year 2010
^ http://www.umm.edu/altmed/drugs/potassium-gluconate-104100.htm
^ ^a ^b ^c ^d Loyola University Chicago Stritch School of Medicine. > EKG Interpretive skills Retrieved on April 22, 2010
^ ^a ^b ^c Poor R-Wave Progression. By: Ross MacKenzie, MD. J Insur Med 2005;37:58–62 [1]
^ ^a ^b Brownfield, J; Herbert, M (2008 Jan). "EKG Criteria for Fibrinolysis: What's Up with the J Point?". The western journal of emergency medicine 9 (1): 40–2. PMC 2672223. PMID 19561701. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2672223. Retrieved 8 October 2011.
^ http://www.monroecc.edu/depts/PSTC/backup/parasec1.htm#JPT
^ Kenneth M Sutin; Marino, Paul L. (2007). The ICU book. Hagerstwon, MD: Lippincott Williams & Wilkins. pp. 356. ISBN 0-7817-4802-X.

UpToDate Contents

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1. 心電図チュートリアル：心電図分析の基本原則 ecg tutorial basic principles of ecg analysis
2. QRS幅の広い頻脈の診断および治療のアプローチ approach to the diagnosis and treatment of wide qrs complex tachycardias
3. QRS幅の狭い頻脈の臨床症状、診断、および評価 clinical manifestations diagnosis and evaluation of narrow qrs complex tachycardias
4. 早期再分極 early repolarization
5. I群抗不整脈薬の主な副作用 major side effects of class i antiarrhythmic drugs

English Journal

The potential role of cardiac resynchronization therapy in acute heart failure syndromes.

Wang NC, Bhattacharya S, Gheorghiade M.SourceCardiovascular Institute, University of Pittsburgh Medical Center, 200 Lothrop Street B-535, Pittsburgh, PA, 15213, USA, wangnc@upmc.edu.
Heart failure reviews.Heart Fail Rev.2011 Sep;16(5):481-90.
Cardiac resynchronization therapy (CRT) has been demonstrated to improve mortality and morbidity in patients with chronic, stable heart failure who have reduced left ventricular ejection fraction and prolonged QRS duration. Patients with acute heart failure syndromes (AHFS) have been excluded from m
PMID 21431357

Effects of HIV Protease Inhibitors on Cardiac Conduction Velocity in Unselected HIV-Infected Patients.

Charbit B, Gayat E, Voiriot P, Boccara F, Girard PM, Funck-Brentano C.Source1] CIC-9304 and UMRS-956, INSERM, Paris, France [2] Department of Pharmacology, Pitie-Salpetriere Hospital, Assistance Publique-Hopitaux de Paris, Paris, France [3] Department of Pharmacology, Faculty of Medicine, UPMC Universite Paris 06, Paris, France.
Clinical pharmacology and therapeutics.Clin Pharmacol Ther.2011 Aug 3. doi: 10.1038/clpt.2011.131. [Epub ahead of print]
We examined the prevalence and the extent of prolongation of the PR and QRS intervals and their relation to anti-HIV treatments and other clinical characteristics in 970 HIV-infected patients, 749 treated with antiretroviral therapy and 221 untreated. Age, body mass index, heart rate, and treatment
PMID 21814195

Japanese Journal

Limitations and Problems of Assessment of Mechanical Dyssynchrony in Determining Cardiac Resynchronization Therapy Indication : Is Assessment of Mechanical Dyssynchrony Necessary in Determining CRT Indication? (Con)

ISHIKAWA Toshiyuki
Circulation journal : official journal of the Japanese Circulation Society 75(2), 465-471, 2011-01-25
… Prolongation of the QRS duration on an electrocardiogram served as an indirect marker to identify mechanical dyssynchrony. … However, RethinQ study demonstrated that patients with heart failure and narrow QRS intervals might not benefit from CRT, even with dyssynchrony. … Current indication including QRS width is recommended as selection criteria to identify patients suitable for CRT. …
NAID 10027427528

Mechanical Dyssynchrony Is Not Everything of Substrate but Is Essential for Cardiac Resynchronization Therapy : Is Assessment of Mechanical Dyssynchrony Necessary in Determining CRT Indication? (Pro)

KANZAKI Hideaki
Circulation journal : official journal of the Japanese Circulation Society 75(2), 457-464, 2011-01-25
… Despite being an invasive treatment, however, the above effects are not observed in 30-45% of patients selected based on the standard criteria that includes New York Heart Association class III or IV heart failure, left ventricular ejection fraction ≤35%, and QRS duration ≥120 or 130ms. From the fact that quantifiable resynchronization was associated with hemodynamic and clinical improvements, it should follow that mechanical dyssynchrony is a critical substrate for the benefits from CRT. …
NAID 10027427462

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