1 st Degree Block Prolonged P-R interval caused by first degree heart block (lead II)

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1 AV Heart Blocks 1 st degree A condition of a rhythm, not a true rhythm Need to always state underlying rhythm 2 nd degree Type I - Wenckebach Type II Classic dangerous to the patient Can be variable (periodic) or have a set conduction ratio (ex. 2:1) 3 rd degree (Complete) dangerous to the patient 215 Atrioventricular (AV) Blocks Delay or interruption in impulse conduction in AV node, bundle of His, or His/Purkinje system Classified according to degree of block and site of block PR interval is key in determining type of AV block Width of QRS determines site of block 216 AV Blocks cont. Clinical significance dependent on: ü Degree or severity of the block ü Rate of the escape pacemaker site Ventricular pacemaker site will be a slower heart rate than a junctional site ü Patient s response to that ventricular rate Evaluate level of consciousness / responsiveness & blood pressure Assume a patient presenting in Mobitz II or 3 rd degree heart block to have an AMI until proven otherwise 217 AV node block occurs when node is damaged First degree AV node block is when conduction thru AV node > 0.2 sec Causes long P-R interval st Degree Block Prolonged P-R interval caused by first degree heart block (lead II) <

2 2 nd Degree Type I Second-degree AV node block is when only 1 out of 2-4 atrial APs can pass to ventricles Causes P waves with no QRS nd Degree Type II (constant) 2 nd Degree Type II (periodic) P Wave PR Interval QRS Characteristics Uniform Narrow & Uniform Missing QRS after every other P wave (2:1 conduction) Note: Ratio can be 3:1, 4:1, etc. The higher the ratio, the sicker the heart. (Ratio is P:QRS) 223 P Wave PR Interval QRS Characteristics Uniform Narrow & Uniform Missing QRS after some P waves 224 continued In third-degree or complete AV node block, no atrial activity passes to ventricles Ventricles are driven slowly by bundle of His or Purkinjes

3 3 rd Degree (Complete) Complete AV block Arrhythmia: conduction failure at AV node 229 AV node block occur when node is damaged First degree AV node block is when conduction through AV node > 0.2 sec Causes long P-R interval Second-degree AV node block is when only 1 out of 2-4 atrial APs can pass to ventricles Causes P waves with no QRS In third-degree or complete AV node block no atrial activity passes to ventricles Ventricles driven slowly by bundle of His or Purkinjes 230 What are the rhythms? AV Block What are the rhythms?

4 What is the rhythm? AV Block n What is the rhythm? AV Block How Can I Tell What Block It Is? Helpful Tips for AV Blocks Second degree Type I Think Type I drops one Wenckebach winks when it drops one Second degree Type II Think 2:1 (knowing it can have variable block like 3:1, etc.) Third degree - complete Think completely no relationship between atria and ventricles 235 badri@gmc 4/18/ Implanted Pacemaker Most set on demand When the heart rate falls below a preset rate, the heart demands the pacemaker to take over Paced Rhythm - 100% Capture 4/18/12 badri@gmc

5 Left Atrial Enlargement 4. Chamber enlargements Prominent terminal P negativity (biphasic) in lead V1 (i.e., "P-terminal force") duration >0.04s, depth >1 mm Left Atrial Enlargement P Pulmonale and P Mitrale Notched/bifid ( M shaped) P wave (P mitrale ) in limb leads with the inter-peak duration > 0.04s (1 mm) 4/18/12 badri@gmc 242 QRS In Hypertrophy RVH Changes A tall positive (R) wave instead of the rs complex normally seen in lead V1 an R wave exceeding the S wave in lead V1 in adults the normal R wave in lead V1 is generally smaller than the S wave in that lead Right axis deviation (RAD) Right ventricular "strain" T wave inversions 4/18/12 badri@gmc 243 5

6 Conditions with Tall R in V1 4/18/12 badri@gmc 245 Left Ventricular Hypertrophy Sokolow & Lyon Criteria (Am Heart J, 1949;37:161) S in V1+ R in V5 or V6 > 35 mm An R wave of 11 to 13 mm (1.1 to 1.3 mv) or more in lead avl is another sign of LVH Others: Cornell criteria (Circulation, 1987;3: ) SV3 + R avl > 28 mm in men SV3 + R avl > 20 mm in women 5. Segment and wave form analysis 4/18/12 badri@gmc 247 RBBB and LBBB LEFT BUNDLE BRANCH BLOCK LBBB 4/18/12 badri@gmc 249 4/18/12 badri@gmc 250 6

7 LEFT BUNDLE BRANCH BLOCK LBBB 4/18/ Hemiblocks Le9 Anterior Hemiblock 4/18/ /18/ Le9 Posterior Hemiblock 4/18/