I don't have first hand experience, but I'd venture a guess that a very perceptive person might be able to tell? There are still p waves in an ekg with block, so the atria are contracting. wild guess on my part :-)
Bradycardia can arise from two general mechanisms. The sinoatrial node may not function properly either as a result of slow generation of impulses or of blocking of the propagation of impulses. As a result, other pacemakers in the heart become responsible for impulse generation, and these have intrinsically slower rates. The condition, while not harmful in and of itself, is usually an indication of problems with the atrial conduction system.
Heart Block is a type of bradycardia that also is called atrioventricular, or AV block. In this condition, the electrical signals that stimulate heart muscle contractions are partially or totally blocked between the upper chambers (atria) and the lower chambers (ventricles). Heart block occurs in 3 different degrees. Certainly the higher the number the more dangerous.
First-degree heart block (also called first-degree AV block). The electrical impulses are slowed as they pass through the conduction system, but all of them successfully reach the ventricles. First-degree heart block rarely causes any symptoms or problems, and well-trained athletes may have this. Medications can contribute to the condition. No treatment is generally necessary for first degree heart block.
Type I second-degree heart block (also known as Mobitz Type I second-degree AV block or Wenckebach AV block). A benign form that usually requires no intervention.
Type II second-degree heart block (Mobitz Type II second-degree AV block) is also a condition in which some of the electrical impulses are unable to reach the ventricles. This condition is less common than Type I, but is generally more serious. In some cases, a pacemaker is implanted to treat the abnormally slow heartbeat that may result from this condition.
Third-degree heart block (also known as complete heart block or complete AV block) is when none of the electrical impulses can reach the ventricles. When the ventricles, (lower chambers), do not receive electrical impulses from the atria (upper chambers), they may generate some impulses on their own called functional or ventricular escape beats. Ventricular escape beats, natural backup signals, usually are very slow, however, and cannot generate the signals needed to maintain full functioning of the heart muscle.
I may have misunderstood your question...I answered thinking that you were looking for a definition. After reading it again, it appears you were asking what it would look like on an EKG.
I have uploaded some rhythm strips (in my photos) displaying all the types of AV Block as well as Bradycardia. Hope that helps you :))
I don't think my question was all that clear because I'm not sure what's on my mind. LOL
So if a heart is beating at an average of 65 bpm then suddenly drops to half speed for 8-10 beats with some presyncope symptoms, do you think that is simply intermittent brady or a spastic kind of heart block (if there is such a thing)? I'm familiar with paroxysmal atrial tachy since I have that. Is there a paroxysmal brady that starts and stops suddenly? I've never heard of such a thing.
It's hard to really say with certainty what is going on. It could be some kind of transient heart block. Have you discussed it with your cardiologist? If this is occuring on a frequent basis he may order a holter, if not he may want you to wear the beloved event monitor.
Loved your reference to "spastic heart block" LOL!
Thanks for your feedback. In other words this isn't something that can be diagnosed based on how it feels. Oh well. I'll stick with my standard health care policy: if I don't pass out, then I don't need to see the doctor. :-) I'm doing fine. LOL
Heart block can cause bradycardia, that's correct.
Short incidents of bradycardia is usually caused by vagal reactions, though. If you get dizzy sitting on the toilet and "pushing too hard" (to use a not very delightful term) that's vagus induced bradycardia, caused by the valsalva maneuver.
Vagal stimulation both reduces sinus node activity AND increases AV conduction time, meaning that high vagal activity actually can cause heart blocks, this is common during deep sleep, and a quite normal phenomenon. It's certainly not easy to know what happens. If your heart rate suddenly drops to exactly half, a reason can be 2:1 AV block. If it's "paroxysmal" increased vagal activity is often the cause.
Another cause can (of course) be ventricular bigeminy.
This is paroxysmal in that it happens while awake and puttering around, not during sleep where I would expect HR to drop. And it only lasts 8-10 beats, enough to make a person think "Uh-oh, I'd better sit down before I fall down." Palpable pulse goes from a nice thump, thump, thump to thump. . . . . . thump. . . . . .thump. But electrically speaking, who knows.
Thank you for the info. I've never heard of high vagal activity triggering heart blocks. Something new for me to learn.