NORMAL ECG AND VENTRICULAR RHYTHMS

Dr YASSIR BIREMA

MRCP CBNC CBCCT

CONDUCTION SYSTEM

Limb leads

• 12-lead configuration, leads I, II and III are called limb leads, they are bipolar leads

• In a 12-lead ECG, all leads besides the limb leads are unipolar (aVR, aVL, aVF, V1to V6).

• Leads aVR, aVL, and aVF are augmented limb leads

Calculating the heart rate

• divide 300 by the number of large boxes between the R waves

Sinus Rhythms

Sinus Rhythms• rhythms which originate at the SA node.

Sinus rhythms generally travel through the entire conduction system without inhibition.

• They are characterized by:• a conducted P-wave • P-R interval between 0.12 and 0.20

seconds • The QRS width should be 0.04 to 0.12

seconds and be all QRS's are preceded by a P-wave.

• Q-T interval of less the 0.40 seconds. • The rate for a normal sinus rhythm is 60 to

90 beats a minute

• Sinus tachycardia• This is just like a normal sinus rhythm

except that the rate is faster than 100 per minute.

SINUS TACHYCARDIA

Sinus bradycardia

• This is just like a normal sinus rhythm except that the rate is slower than 60 per minute.

Sinus bradycardia

SINUS ARRHYTHMIA

Ventricular rhythms

Premature Ventricular Contractions

• ventricular cell may initiate an impulse and cause a contraction

• caused by a variety of conditions including respiratory problems and stress

• there will be a compensatory pulse with a PVC

• PVCs are classified on the basis of their origin

• Unifocal PVCs originate from the same focus.

• They all have the same shape, or morphology.

• Multifocal PVCs arise from multiple focii. Each focus has a unique morphology. Often, there will be a repeating sequence, indicating several specific focii.

• Make an effort to note the number and

• PVCs are also classified by their frequency

• Bigeminy, trigeminy, etc... • If each normal contraction is followed by a

single PVC, we call this bigeminy. • If two normal contractions are followed by

a single PVC, we have trigeminy• Couplets• Exactly two PVCs in a row is called a

couplet

BIGEMINY

TRIGEMINY

COUPLET

Ventricular Tachycardia

• V-Tach is a rapid dysrhytmia in which the ventricles depolarize very quickly and without regard for the atria.

• V-Tach is actually said to happen whenever three or more PVS occur in a row (which is why we don't name anything beyond a couplet).Regarding pulses, any of the following could happen:

• pulse for every complex - the pulses will be weak and cardiac output low.

• pulse for some beats - this is ominous • no pulse - there may or may not be any

contraction at all, but if there's no pulse, you're patient is in bad shape.

• Associated symptoms — ranging from none to hemodynamic collapse and sudden cardiac arrest

• VT rhythms have rates between 100 and 280 beats per minute and can be monomorphic or polymorphic

• VT generally has a wide QRS complex (fascicular VT rhythms are an exception, with QRS durations less than 120-140 ms)

• Ventricular tachycardia• Monomorphic• Polymorphic• Aberrancy with PSVT

(LBBB/RBBB/IVCD)• Accessory pathway with PSVT

SVT WITH ABERRANCY

Antidromic Reciprocating Tachycardia

WBW

VENTRICULAR TACHYCARDIA

• Clinical• History of coronary artery disease or heart

failure• Cannon a waves in jugular venous pulse

contour• Variable first heart sound on auscultation

Features Favoring VT Over PSVT

• ECG• AV dissociation• Fusion beats• Capture beats• QRS duration >140-160 ms• Precordial concordance• Northwest axis• ECGLead V6 QRS with rS or S

morphology

CAPTURE BEAT

FUSION BEAT

DISTINCT CLINICAL SYNDROMES OF VT

• Ischemia and Acute Post–Myocardial Infarction VT

• VT in Arrhythmogenic Right Ventricular Dysplasia,Hypertrophic Cardiomyopathy, and Infiltrative Diseases of the Heart

• Familial Channelopathy Syndromes• Idiopathic VT in the Patient With a

Structurally Normal Heart and No Repolarization Abnormalities

• 1/Adenosine-Sensitive VT, arise in RVOT

• 2/Verapamil-Sensitive Intrafascicular VT

Scar of Ischemia as a site of VT

ARVD

HCOM

Idiopathic left ventricular tachycardia

VT

Ventricular Fibrillation• V-fib is the most common fatal dysrhytmia in adult

patients. • V-fib represents a chaotic depolarization of

random ventricular cells. • A heart in V-fib literally looks like jiggling Jell-o.

There is no pulse associated with this rhythm. CPR won't do much good either, nor will most drugs.

• You'd better hope the defibrillator works!• V-Fib is usually described as coarse or fine . • Generally, as the tissue dies, the voltage

decreases, hence, coarse is a little better than fine V-Fib.

VF