مرسمة كهربائية القلب

مرسمة كهربائية القلب تقوم بالتقاط وتسجيل التيارات التي يولدها القلب. يتم التقاط هذه التيارات بوساطة أقطاب كهربائية لها شرائط فلزية موصلة للكهرباء تُلصق بجسم المريض. وتقوم المرسمة بتكبير هذه التيارات وتسجيلها على هيئة خطوط موجية.

12 Lead ECG of a 26-year-old male.

Image showing a patient connected to theعشرة electrodes necessary for a 12-lead ECG

مرسمة كهربائية القلب Electrocardiography جهاز قياس يستخدم لتشخيص اضطرابات القلب. ففي جميع مرة يدق فيها القلب تنتج تيارات كهربائية. وتلتقط مرسمة كهربائية القلب هذه التيارات وتسجلها على ورق. ويسمى هذا الإنضمام رسم كهربائية القلب، ويمكن توصيل المرسمة إلى راسمة ذبذبات وهي جهاز قياس يعرض التيارات على شاشة تلفازية.تحتوي مرسمة كهربائية القلب على معدات تكبير وتسجيل. وتمر الأسلاك من المرسمة إلى أقطاب كهربائية، وهي شرائط فلزية موصلة للكهرباء. ويسجل رسم كهربائية القلب بإلصاق الأقطاب الكهربائية بجلد المريض بوساطة مادة هلامية خاصة. وتوضع الأقطاب على جميع ذراع وساق وعند ستّ نقاط على الصدر، فوق منطقة القلب.

One second of ECG graph paper

وتقوم الأقطاب بالتقاط التيارات التي ينتجها القلب عند جميع خفقة من خفقاته، وتنقلها إلى مكبر داخل مرسمة القلب. تنساب التيارات المكبرة بعد ذلك خلال ملف من سلك رفيع جدًا معلق داخل مجال مغنطيسي، ويتحرك السلك بسبب تفاعل هذه التيارات مع المجال المغنطيسي. وتقوم رافعة حساسة بتسجيل حركة السلك على ورق رسم بياني متحرك فينتج عن ذلك رسم كهربائية القلب. تنتج جميع نبضة قلب سلسلة من الخطوط الموجية. ويعطي النبض الطبيعي للقلب نموذجًا موجيًا محددًا. وتغير أنواع معينة من أمراض القلب هذا النموذج المعروف على نحويمكن التعهد عليه.

Proper placement of the limb electrodes, color coded as recommended by the American Health Association (a different colour scheme is used in Europe). Note that the limb electrodes can be far down on the limbs or close to the hips/shoulders, but they must be even (left vs right).

12 leads

Electrode label (in the USA)	Electrode placement
RA	On the right arm, avoiding bony prominences.
LA	In the same location that RA was placed, but on the left arm this time.
RL	On the right leg, avoiding bony prominences.
LL	In the same location that RL was placed, but on the left leg this time.
V₁	In the fourth intercostal space (between ribs أربعة & 5) just to the right of the sternum (breastbone).
V₂	In the fourth intercostal space (between ribs أربعة & 5) just to the left of the sternum.
V₃	Between leads V₂ and V₄.
V₄	In the fifth intercostal space (between ribsخمسة & 6) in the mid-clavicular line (the imaginary line that extends down from the midpoint of the clavicle (collarbone)).
V₅	Horizontally even with V₄, but in the anterior axillary line. (The anterior axillary line is the imaginary line that runs down from the point midway between the middle of the clavicle and the lateral end of the clavicle; the lateral end of the collarbone is the end closer to the arm.)
V₆	Horizontally even with V₄ and V₅ in the midaxillary line. (The midaxillary line is the imaginary line that extends down from the middle of the patient's armpit.)

الإستخدامات

يستخدم الأطباء مرسمة كهربائية القلب في تشخيص أمراض القلب الناتجة عن ازدياد ضغط الدم والحمى الروماتزمية والعيوب الولادية. وغالبًا ما يؤخذ رسم كهربائية القلب والمريض مُسْتَلْق على الفراش. ويسمى هذا الأسلوب رسم كهربائية القلب عند الراحة. وقد تؤخذ هذه الصورة أثناء قيام المريض بمجهود، ويسمى هذا الاختبار رسم كهربائية القلب عند الإجهاد. وهويبين ما إذا كان القلب يتلقى كمية كافية من الأكسجين أثناء النشاط العنيف. يستخدم الأطباء رسم كهربائية القلب عند الإجهاد في تشخيص سقم الشرايين التاجية الذي تكون فيه الشرايين التي تغذي عضلة القلب قد ضاقت إلى حد خطير بحيث تحد من سريان الدم.

Schematic representation of normal ECG

Animation of a normal ECG wave.

Detail of the QRS complex, showing ventricular activation time (VAT) and amplitude.

تاريخ

تم اختراع مرسمة كهربائية القلب المطورة من المقياس الجلفاني الخيطي في سنة 1903م بوساطة عالم وظائف الأعضاء الهولندي فيلم أينتهوفن.

Feature	Description	Duration
RR interval	The interval between an R wave and the next R wave is the inverse of the heart rate. Normal resting heart rate is between 50 and 100 bpm	0.6 to 1.2s
P wave	During normal atrial depolarization, the main electrical vector is directed from the SA node towards the AV node, and spreads from the right atrium to the left atrium. This turns into the P wave on the ECG.	80ms
PR interval	The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex. The PR interval reflects the time the electrical impulse takes to travel from the sinus node through the AV node and entering the ventricles. The PR interval is therefore a good estimate of AV node function.	120 to 200ms
PR segment	The PR segment connects the P wave and the QRS complex. This coincides with the electrical conduction from the AV node to the bundle of His to the bundle branches and then to the Purkinje Fibers. This electrical activity does not produce a contraction directly and is merely traveling down towards the ventricles and this shows up flat on the ECG. The PR interval is more clinically relevant.	50 to 120ms
QRS complex	The QRS complex reflects the rapid depolarization of the right and left ventricles. They have a large muscle mass compared to the atria and so the QRS complex usually has a much larger amplitude than the P-wave.	80 to 120ms
J-point	The point at which the QRS complex finishes and the ST segment begins. Used to measure the degree of ST elevation or depression present.	N/A
ST segment	The ST segment connects the QRS complex and the T wave. The ST segment represents the period when the ventricles are depolarized. It is isoelectric.	80 to 120ms
T wave	The T wave represents the repolarization (or recovery) of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred to as the relative refractory period (or vulnerable period).	160ms
ST interval	The ST interval is measured from the J point to the end of the T wave.	320ms
QT interval	The QT interval is measured from the beginning of the QRS complex to the end of the T wave. A prolonged QT interval is a risk factor for ventricular tachyarrhythmias and sudden death. It varies with heart rate and for clinical relevance requires a correction for this, giving the QTc.	300 to 430ms^[]
U wave	The U wave is not always seen. It is typically low amplitude, and, by definition, follows the T wave.
J wave	The J wave, elevated J-Point or Osborn Wave appears as a late delta wave following the QRS or as a small secondary R wave . It is considered pathognomic of hypothermia or hypocalcemia.

Graphic showing the relationship between positive electrodes, depolarization wavefronts (or mean electrical vectors), and complexes displayed on the 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.

Normal	−30° to 90°	Normal	Normal
Left axis deviation	−30° to −90°	May indicate left anterior fascicular block or Q waves from inferior MI.	Left axis deviation is considered normal in pregnant women and those with emphysema.
Right axis deviation	+90° to +180°	May indicate left posterior fascicular block, Q waves from high lateral MI, or a right ventricular strain pattern.	Right deviation is considered normal in children and is a standard effect of dextrocardia.
Extreme right axis deviation	+180° to −90°	Is rare, and considered an 'electrical no-man's land'.

Diagram showing the contiguous leads in the same color

Category	Color on chart	Leads	Activity
Inferior leads	Yellow	Leads II, III and aVF	Look at electrical activity from the vantage point of the inferior surface (diaphragmatic surface of heart).
Lateral leads	Green	I, aVL, V₅ and V₆	Look at the electrical activity from the vantage point of the lateral wall of left ventricle. The positive electrode for leads I and aVL should be located distally on the left arm and because of which, leads I and aVL are sometimes referred to as the high lateral leads. Because the positive electrodes for leads V5 and V6 are on the patient's chest, they are sometimes referred to as the low lateral leads.
Septal leads	Orange	V₁ and V₂	Look at electrical activity from the vantage point of the septal wall of the ventricles (interventricular septum).
Anterior leads	Blue	V₃ and V₄	Look at electrical activity from the vantage point of the anterior surface of the heart (sternocostal surface of heart).

Shortened QT interval	Hypercalcemia, some drugs, certain genetic abnormalities.
Prolonged QT interval	Hypocalcemia, some drugs, certain genetic abnormalities.
Flattened or inverted T waves	Coronary ischemia, left ventricular hypertrophy, digoxin effect, some drugs.
Hyperacute T waves	Possibly the first manifestation of acute myocardial infarction.
Prominent U waves	Hypokalemia.

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المصادر

الموسوعة المعهدية الكاملة

^ [1]^[]
^ Gan-Xin Yan; Charles Antzelevitch. Cellular Basis for the Electrocardiographic J Wave. Circulation. 1996;93:372-379. http://circ.ahajournals.org/cgi/content/full/circulationaha;93/2/372

وصلات خارجية

Electrocardiogram, EKG, or ECG – Explanation of what an ECG is, who needs one, what to expect during one, etc. Written by the National Heart Lung and Blood Institute (a division of the NIH)
University of Maryland School of Medicine Emergency Medicine Interest Group – Introduction to EKGs as written by a medical student and a cardiologist
ECG in 100 steps: Slideshow
ECG Lead Placement – A teaching guide "designed for student nurses who know nothing at all about Cardiology"
ECGpedia: Course for interpretation of ECG
12-lead ECG library
Simulation tool to demonstrate and study the relation between the electric activity of the heart and the ECG
Minnesota ECG Code
openECGproject - help develop an open ECG solution
EKG Review: Arrhythmias – A guide to reading ECGs not written for a university biology (anatomy and physiology) course.

نطقب:Electrodiagnosis