does ventricular tachycardia always cause a weaker pulse, or could the pulse be of normal intensity or even forceful?
- JasonLv 73 weeks ago
In true VT, the pulse is weaker because of decreased diastolic filling time and the lack of atrial kick.
The time it takes for the heart to contract is pretty much the same no matter how fast it's beating. What changes is the amount of time BETWEEN contractions. That period is called diastole. During diastole, blood passively flows from the atria to the ventricles. The atria then contract, forcing more blood into the ventricles which then contract. That's referred to as "atrial kick." The more time during diastole, the more time the blood has to passively move from the atria to the ventricles.
When the heart rate speeds up, there is less time for passive filling. The atria have to do more of the work of filling the ventricles -- but they are a fraction of the volume of the ventricles. They help BOOST the amount of blood in the ventricles, but they can't fill them on their own. There still needs to be some diastolic filling time.
When the heart rate gets too high, there simply isn't enough time for the ventricles to fill. They are contracting so fast they never get any resting time to passively fill. If there is less blood going in, then there is less blood coming out -- which decreases the strength of the pulse.
This is why at a very high heart rate, you may feel no pulse at all. There is simply no time for the ventricles to fill.
.Source(s): Respiratory therapist (B.S., RRT, RPFT) Working on my master's in nursing.