Natalia Fernandez, PT, MS, MSc, CCS University of Michigan Health Care System Department of Physical Medicine and Rehabilitation.

Premature Atrial Contractions A Premature Atrial Contraction (PAC) occurs when a focus in the atrium other than the SA node generates an action potential before the next scheduled SA node action potential. There are four main characteristics of PACs: 1. Premature 2. Ectopic 3. Narrow complexes (QRS <.12 sec) 4. Compensatory pause

Premature Atrial Contractions Defining Criteria and ECG features Underlying Rhythm: Usually Regular Rate: normal or accelerated (underlying rhythm dependent) P waves: different morphology than sinus P wave, (premature and abnormal in size, shape and direction as ectopic pacemaker) PR interval: normal vs. not measureable QRS: <.12sec

Supra Ventricular Tachycardia (SVT) Defining Criteria and ECG features Rate: seldom <150 per minute, often up to 250 per min Rhythm: regular P wave: hidden PR interval: not measureable QRS: normal, narrow (usually <.12sec)

Supra Ventricular Tachycardia (SVT) Clinical Manifestations: Palpitations felt at onset by patients Anxious Uncomfortable Low exercise tolerance at high rates Common Etiologies: Accessory conduction pathways In healthy people reentry SVT provoked by caffeine, hypoxia, cigarettes, stress, anxiety, sleep deprivation, medication Frequency of SVT is increased in unhealthy patients with CAD, chronic obstructive pulmonary disease and CHF.

Heart Block Second degree Type I -Mobitz I or Wenchebach Defining Criteria and ECG features: Rhythm: Regular atrial rhythm; irregular ventricular rhythm Rate: variable P waves: Sinus (normal morphology with constant P-P interval) PR interval: progressively lengthening of PR interval from cycle to cycle; then one P wave not followed by QRS complex (“dropped beat”) QRS complex: Normal (0.10 second or less) but QRS “drops out” periodically

Heart Block Second degree Type I -Mobitz I or Wenchebach Clinical Manifestations: Rate-related Most often asymptomatic Symptoms: chest pain, SOB, decreased level of consciousness Signs: hypotension, shock, pulmonary congestion, CHF, angina Common Etiologies: AV nodal blocking agents : beta-blockers, non – dihydropyridine calcium channel blockers, digoxin Conditions that stimulate the parasympathetic nervous system Acute coronary syndrome that involves the R coronary artery

Heart Block Second degree Type II -Mobitz II Defining Criteria and ECG features: Rhythm: Regular atrial rhythm; irregular ventricular rhythm Rate: Atrial rate: usually per minute (underlying sinus rhythm) Ventricular rate: slower than atrial rate P waves: Sinus; some P waves will not be followed by QRS complex PR interval: may be normal or prolonged; but is constant. QRS complex: Normal or wide

Heart Block Second degree Type II -Mobitz II Clinical Manifestations: Symptoms: chest pain shortness of breath, decreased level of consciousness Signs: hypotension, shock, pulmonary congestion, CHF, AMI Common Etiologies: Acute coronary syndrome that involves braches of left coronary artery

Heart block – Third Degree Rhythm: Regular atrial and ventricular rhythm Rate: Atrial: bpm Ventricular: bpm P waves: sinus, have no relationship to the QRS complex PR interval: there is no relationship between P wave and R wave QRS complex: Normal or wide

Heart block – Third Degree Clinical Manifestations: Symptoms: chest pain shortness of breath, decreased level of consciousness Signs: hypotension, shock, pulmonary congestion, CHF, AMI Common Etiologies: Acute coronary syndrome that involves braches of left coronary artery.

Heart Block

Bundle Branch Blocks Defining Criteria and ECG features: Rhythm: regular (regular or irregular depending on underlying rhythm) Rate: that of the underlying rhythm P waves: sinus (normal if underlying rhythm is sinus) PR interval: normal ( sec) QRS complex: wide (0.12 second or greater)