Nice, clear example of ventricular bigeminy with an underlying sinus rhythm. We do not know from this strip if the sinus rhythm is a bradycardia at a rate of about 42 per minute, or if the underlying sinus rhythm is actually at a rate of 85 per minute, with every other sinus beat inhibited by the occurance of a PVC. In the first possibility, the ventricular beats would be considered "escape" beats, positively contributing to the patient's heart rate. In the second instance, the rather late-occurring PVCs would cause the heart to be refractory, preventing the sinus P wave from conducting it's impulse to the ventricles. Sometimes, we can see signs of the sinus P wave "hiding" in the PVC, but in this case, if P waves exist, they fall almost exactly in the middle of the ventricular beats' QRS complex, making them invisible. A good strategy would be to watch the strip continuously for some time, hoping to catch the conduction of two sinus beats in a row, solving the dilemma.
This is a nice example of sinus rhythm with ventricular bigeminy in a patient with intermittent chest pain and hypertension. The underlying rhythm is most likely normal sinus rhythm, but every other sinus P wave is most likely hidden in the PVCs, and not conducted due to the refractory state of the ventricles after the PVCs. Often, signs of the "hidden" P waves will show in some leads, but that is difficult to demonstrate here.
It may be difficult to be sure of an adequate underlying rate, so the PVCs should not be eliminated with antiarrhythmic drugs until there is some ECG sign of a normal underlying rate.
Remember, the fourth channel on this ECG is a Lead II rhythm strip. So, if you teach rate and rhythm monitoring, and don't want to use a 12-Lead ECG for your students, simply crop the bottom strip for your class.
This ECG is from an elderly man who is being worked up for general weakness in the Emergency Department. Every other beat is a PVC (ventricular bigeminy). Even though he appears to have a very slow sinus rhythm underlying the bigeminy, often the PVCs are taking the place of one of the sinus beats by occurring early in the cycle and making the ventricles refractory to the next sinus impulse. If you look carefully at leads that show P waves well, like II and III in this case, you will see a slight disturbance in the T wave of the PVC, marking where the sinus P wave occurs. Try marching out the P waves you can see, and look for the hidden P waves at the halfway point between them.