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Ventricular Rhythms

The largest portions of the heart, the ventricules, are the areas most dangerous problems occur. Since it is the largest part of the muscle, it does the most work to move the blood. In a normal contraction the impulse passes through the ventricles quickly, about 0.04 to 0.12 seconds as we measure it on the ECG, (Electrocardiogram.) An interval larger then those can be seen when a block occurs somewhere along the bundle branches, causing a wider qrs then normal.

Bundle Branch Block

It is possible to have a normal sinus rhythm with a bundle branch block. The p-r interval would be normal and the rate within 60 to 100 beats a minute but the qrs is longer then 0.12 seconds.

Premature Ventricular Contractions

The ventricle may contract earlier then expected in the normal cycle without seriously interrupting the normal sequence. Many such pvc's are benign and can just be watched. The wave forms will be wider then normal for a qrs and generally occur with a compensatory pause. Interpolated pvc's are when there is no compensatory pause. The dangerous part is learning which are ok and which are bad. Don't think that by viewing this page you will be ready to distinguish those subtle differences, it takes more time then I have here to help you with that. We can at least define the various rhythms you will see.

Unifocal PVC
Text Version When a pvcs occurs they may come from one source or many different sources. With a single impulse point the extra wave forms will be uniform in shape and size.

Multifocal PVC
Text Version When there are different places starting the early impulse the pattern will differ from one pvc to the next. The sequence of occurrence is important in defining these arrythmias.

Text Version When the frequency of the pvc's is once every other beat, we call it bigeminy. At the number of beats between increases to three we can call it trigeminy. Here we see an example of bigeminy

Text Version The grouping of two pvc's in sequence can be called a couplet.

R on T Phenomena
Text Version If the pvc occurs on a dangerous point of the t-wave, (remember the refractory period we discussed earlier,) the early beat could upset the whole system and cause the ventricles to contract rapidly in ventricular tachycardia.

Remember to always evaluate the patient first! The other information is just data, the patient comes first!

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Last Updated by Nurse George on 04/02/01