Title: Marked First Degree AV Block<br/>Author: Ali Farzad<br/><a href='http://umem.org/profiles/faculty/737/'>[Click to email author]</a><hr/><p class="p1">
        <span style="font-size:14px;">First-degree atrioventricular (AV) block is defined as an abnormally prolonged PR-interval >200ms. Although traditionally considered to be a benign clinical entity, not all first degree AV blocks are treated the same.  </span></p>
<p class="p1">
        <span style="font-size:14px;">Markedly prolonged PR-intervals (PR >300ms) can cause symptoms and hemodynamic compromise due to inadequate timing of atrial and ventricular contractions. Consider the following ECG from a 32 YOF with intermittent episodes of syncope and dizziness…</span></p>
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        <span style="font-size:14px;"><img alt="" src="https://umem.org/files/uploads/content/ECG%20Challenge/Marked%201st%20degree%20AVB.jpg" style="width: 560px; height: 331px;" /></span></p>
<p class="p4">
        <span style="font-size:14px;">There is marked first degree AV block (PR=434 ms). When the PR-interval gets too long, AV dyssynchrony compromises ventricular filling and decreases cardiac output, similar to the so-called <a href="http://emedicine.medscape.com/article/159706-overview"><span style="color:#0000cd;">p</span></a><a href="http://emedicine.medscape.com/article/159706-overview"><span style="color:#0000cd;"><span class="s1">acemaker syndrome</span></span></a>.</span></p>
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        <span style="font-size:14px;">Current ACC/AHA guidelines state that permanent pacemaker implantation is reasonable for marked first degree AV block with hemodynamic compromise or symptoms similar to those of pacemaker syndrome. (Class IIa, Level of Evidence B). The guidelines caution that pacemakers are not indicated in asymptomatic patients with isolated first degree AV block.</span></p>
<fieldset><legend>References</legend>

                <p>
        Special thanks to Dr. Brandon Cole for submitting the ECG</p>
<p>
        <strong>References / Further Reading (Attached)</strong></p>
<p>
        <span style="font-size: 12px;">First-Degree AV Block-An Entirely Benign Finding or a Potentially Curable Cause of Cardiac Disease? </span><i style="font-size: 12px;">Annals of Noninvasive Electrocardiology</i><span style="font-size: 12px;">.2013;18(3):215–224. doi:10.1111/anec.12062.</span></p>
<p>
        <span style="font-size: 12px;">ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. </span><i style="font-size: 12px;">Circulation</i><span style="font-size: 12px;">. 2008;117(21):e350–e408. doi:10.1161/CIRCUALTIONAHA.108.189742.</span></p>
</fieldset><fieldset><legend>Attachments</legend>
                        1st_Degree_AV_Block—Benign_or_Curable_Cardiac_Disease?.pdf (253 Kb)<br/><a href='http://umem.org/files/uploads/1310272020_1st_Degree_AV_Block—Benign_or_Curable_Cardiac_Disease?.pdf' target='_blank'>http://umem.org/files/uploads/1310272020_1st_Degree_AV_Block—Benign_or_Curable_Cardiac_Disease?.pdf</a><br/><br/>
                        ACC:AHA_Pacemaker_Guidelines.pdf (1524 Kb)<br/><a href='http://umem.org/files/uploads/1310272020_ACC:AHA_Pacemaker_Guidelines.pdf' target='_blank'>http://umem.org/files/uploads/1310272020_ACC:AHA_Pacemaker_Guidelines.pdf</a><br/><br/></fieldset>