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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
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