AV block and ST elevation https://www.ecgguru.com/taxonomy/term/768/all en ECG Basics: 2:1 AV Block https://www.ecgguru.com/ecg/ecg-basics-21-av-block <div class="field field-name-field-ecg field-type-image field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/ecg/ecg-basics-21-av-block"><img typeof="foaf:Image" src="https://www.ecgguru.com/sites/default/files/AVB%202%20to%201%20----0.jpg" width="2066" height="330" alt="" /></a></div></div></div><div class="field field-name-field-ecg-interpretation field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Second-degree AV block can either be Type I (Wenckebach) or Type II.&nbsp; In either case, some P waves are conducted to the ventricles, and some are not. Type I blocks usually occur in the AV node, and are often benign. Type II blocks are more often "sub-Hisian", or fascicular blocks, and are more likely to progress to higher levels of AV block and bradycardia.&nbsp; When a second-degree AVB is conducted in a 2:1 ratio, it is difficult to differentiate Type I from Type II.&nbsp; Features that favor the diagnosis of Type I are narrow QRS complex and the non-conducted P waves land on the previous T waves - during the refractory period of the ventricles.</p><p>Type II blocks are more likely to have a wide QRS with a bundle branch block morphology.&nbsp; That is because Type II blocks often reflect serious fascicular disease.&nbsp; A typical Type II block is a persistent bifascicular block (ex: RBBB and left anterior hemiblock)) with an <strong>intermittent </strong>block in the third fascicle.&nbsp; Another way to think of it is an intermittent tri-fascicular block. If that one remaining fascicle stops conducting, the patient will be in complete heart block.</p><p>Signs of Type II blocks include the wide QRS and also two or more non-conducted P waves in a row.&nbsp; Also, P waves that are "out in the open", away from the refractory period, but fail to conduct are an ominous sign.</p><p><span style="font-size: 13.008px;">One strategy for reacting to a 2:1 block is to first assess the ventricular rate (54 bpm in this example).&nbsp; Determine if it is adequate for the patient's hemodynamic stability.&nbsp; If not, act to increase the rate.&nbsp; Otherwise, it may be prudent in the stable patient to watch the rhythm strips for a while.&nbsp; Sometimes, two p waves in a row will conduct - unmasking either progressive prolongation of the PR interval (Type I) or stable PR intervals (Type II).&nbsp;</span></p><p><span style="font-size: 13.008px;">The patient in this example was having an inferior wall M.I.&nbsp; The ST elevation will not always show up on a monitor strip, as it does here.&nbsp; A 12-lead ECG is the minimum standard for evaluating for coronary artery disease and acute M.I.&nbsp; It is possible that the 2:1 block will disappear when the atrial rate (about 108 here) is slowed.</span></p></div></div></div> Fri, 07 Jun 2019 21:48:59 +0000 Dawn 770 at https://www.ecgguru.com