Basic Electrocardiography.ppt

1、Basic Electrocardiography,Ventricular Rhythms/Arrhythmias,Ventricular Rhythms/Arrhythmias:,The ventricles depolarize before the atria. (Atria may or may not depolarize) The origin of the beat(s) is below the Bundle of HIS Since the impulse originates in one of the ventricles, it will take longer tha

2、n .12 seconds to depolarize. (hintboth ventricles are NOT depolarizing simultaneously) Therefore, the QRS complexes will measure greater than .12 sec. (“wide, fat, and ugly”),Premature Ventricular Contractions:,Also called “PVCs”, these originate from a single ectopic focus in the ventricles that fi

3、res early, creating an “early” or premature beat. Rhythm: irregular; an early beat upsets the underlying rhythm. There will usually be a compensatory pause. Rate: variable; depends on underlying rhythm P waves: the early beat does not have a P wave.,PVCs, continued:,PRI: since the early beat does no

4、t have a P wave, there is no PR interval. Other PR intervals can be normal (of underlying rhythm) QRS: will be greater than .12 sec. It will often look quite different than underlying QRS complexes. The T wave is often in the opposite direction of the QRS.,PVCs, continued:,PVCs can also be “interpol

5、ated”, meaning that they occur in between two regular beats. PVCs that come from one single focus are Unifocal PVCs. All PVCs will look alike. PVCs that come from two or more foci are called “multifocal” PVCs. They will have different QRS configurations, but all will be greater than .12 sec.,PVCs, c

6、ontinued:,R on T PVCs are those beats in which the R wave of the PVC is occuring on or near the T wave of the preceeding beat. A pair of PVCs is called a Couplet.,PVCs, continued:,PVCs can occur in patterns: Bigeminy: every other beat is a PVC Trigeminy: one PVC for each two normal beats Quadrigemin

7、y: one PVC for each three normal beats A “run of PVCs” is three or more consecutive PVCs (also called V-Tach),Significance of PVCs,Indication of irritability in the ventricles (many causes) Frequent PVCs can decrease cardiac output. Atria usually will not depolarize. Can lead to more serious ventric

8、ular arrhythmias, such as V-TAC. There are multiple causes of PVCs. May occur in individuals with a healthy heart as well as those with heart disease.,When to be concerned about PVCs,Greater than 8-10 per minute Couplets and/or multifocal Bigeminal or Trigeminal pattern “R on T” PVC”sthose that occu

9、r close to or on the T wave of the preceeding beat. Treatment is geared towards the underlying cause and symptoms (if any).,Ventricular Tachycardia:,A sustained run of PVCs. Rhythm: usually regular Rate: 150-250 (but can be slower) P waves: none PRI: none QRS: all complexes wide and bizzare (“fat an

10、d ugly”), greater than .12 sec.,Significance of VTACH,TROUBLE: rapid loss of cardiac output. Check for a pulse! If conscious; immediate drug therapy (if hemodynamically stable), if not; then cardioversion/defibrillation.,Ventricular Fibrillation:,A lethal arrhythmia: essentially there is no pulse or

11、 cardiac output. Rhythm: none Rate: none P waves: none PRI: none QRS: no clearly discernable QRS complex; wave forms look chaotic.,Ventricular fibrillation,Two types: Fine: can look like A-fib without QRS complexes, amplitude of waves 3mm,Significance of V-Fib,Ooohthis is very bad! There is NO PULSE

12、 and NO CARDIAC OUTPUT! Treatment is CPR or defibrillation.ASAP Drugs needed, Airway needed This is where ACLS comes in Hope and pray that some type of more normal rhythm is restored.but often it doesnt.,Ideoventricular Rhythm (or ventricular escape rhythm),The ventricles are pacing the heart (not a

13、 good thing!) Both SA node and AV node have failed. Rhythm: regular (usually) Rate: 20-40 Accelerated IVR: 40-100 P waves: none (or you might see what looks like Pwaves, but isnt) PRI: none QRS: each QRS complex measures greater than .12 (wide, “fat and ugly”),Significance of IVR,Causes: Extensive m

14、yocardial damage (usually as a result of an MI), and/or failure/block of SA and AV node Significance: Ooooh.we have big problems! (Both you and the patient!) You: Check for a pulse! Patient will not have much cardiac output. Pacemaker.drugs.? “Agonal” rhythm= with rate below 20bmp,Asystole:,The heart is electrically silent (cardiac standstill) There is no pulse, no car