Chapter 12 – Miscellaneous Conditions

1. Chapter 12 – Miscellaneous Conditions Artifact Digitalis Effect Pericarditis Early Repolarization Low Voltage Hypo- and Hypercalcemia Hyperkalemia Wolff-Parkinson-White Pulseless Electrical Activity

2. Artifact • Causes and Cures • Inspect multiple leads • Figure 12.1, page 135

3. Digitalis Effect • Often used to treat CHF • U shape depression of the ST segment. • Does not indicate toxicity • Problem: Difficult in determining if ST changes are caused by ischemia or Digitalis. • Toxicity problems include seizures, anorexia nervosa, nausea, tremors, etc. • Figure 12.2, page 136

4. Early Repolarization • > 1mm ST segment elevation in a normal person (ST ELEVATION = Infarct) • Normal variant caused by unusually fast repolarization of the ventricles. • Brief upward deflection in one or more leads at the J point (where the QRS complex ends and ST segment begins). • Does not occur in multiple leads or change over time. • Figure 12.4, Page 138

6. Low Voltage • Criteria: Total QRS < 5 mm voltage in each limb lead and < 15mm voltage in each precordial lead. • Surface current recorded by electrodes is below normal. • May be normal or due: • to subcutaneous fat • Increased intrathoracic air volume (emphysema) • Infarction (death of myocardial cells)

7. Possible Low Voltage

8. Normal ECG

9. Hypo- and Hypercalcemia • Hypocalcemia prolongs the QT interval. No specific guidelines. • Hypercalcemia shortens the QT interval (beginning of the T wave comes right after the QRS. • QT INTERVAL: Beginning of QRS complex to the end of the T wave • Figure 12.4, Page 138

10. Hyperkalemia • Elevated plasma potassium. • Tall Peaked waves initially (T waves should only be 1/3 the height of the QRS). • With continued rise in potassium T waves remain tall and peaked and what appears to be an idioventricular rhythm appears. • Figure 12.7, page 140. A: Early, B: Progressing

11. Progressing Hyperkalemia., Figure 12.7, Page 140. Ideoventricular rhythm: Wide QRS, impulse is transmitted through the ventricles.

12. Wolff Parkinson-White Syndrome • Some patients have an accessory or additional pathway to the AV Node from the SA Node. • May be present all the time or intermittent. • Depolarization from Atria to Ventricles travels two paths – Bundle of His and now Kent Bundle (this pathway is more RAPID). No Delay. • They then join together at the beginning of Ventricular depolarization.

13. Wolff-Parkinson-White • Figure 12.10, Page 143 • Three characteristics: • A: Short PR interval • B: Wide QRS complex • C: Delta Wave • These characteristics are not present in all leads. Not in book

14. WPW • Can cause a rapid heart rate (tachycardia). • Can be congenital but occurs mostly in adults age 30-40. • Therapy can include the valsalva manuever, medications, cardioversion, ablation or surgery. Many people with this syndrome who have symptoms or episodes of tachycardia (rapid heart rhythm) may have dizziness, chest palpitations, fainting or, rarely, cardiac arrest. Other people with WPW never have tachycardia or other symptoms.

15. Figure 12.11, page 144

16. Figure 5.4 Clinical Exercise Physiology TextbookWolff Parkinson-White Syndrome http://medmovie.com/mmdatabase/mediaplayer.aspx?Message=VG9waWNpZD02ODQ7Q2xpZW50SUQ9NjU7VmVybmFjdWxhcklEPTE%3D%2DyHFV6XkUe9M%3D

17. What is this rhythm?

19. Pulseless Electrical Activity - EMD • Normal or somewhat normal ECG but mechanical functioning is severely impaired. Can be any rhythm. • The ECG and contractile activity are closely coupled but are not synonymous. • Perfusable rhythm but no pulse or measureable blood pressure. • Must correlate with clinical activity.

20. WPW • If there's an extra conduction pathway, the electrical signal may arrive at the ventricles too soon. This condition is called Wolff-Parkinson-White syndrome (WPW). It's in a category of electrical abnormalities called "pre-excitation syndromes." • It's recognized by certain changes on the electrocardiogram, which is a graphical record of the heart's electrical activity. The ECG will show that an extra pathway or shortcut exists from the atria to the ventricles. • Many people with this syndrome who have symptoms or episodes of tachycardia (rapid heart rhythm) may have dizziness, chest palpitations, fainting or, rarely, cardiac arrest. Other people with WPW never have tachycardia or other symptoms. About 80 percent of people with symptoms first have them between the ages of 11 and 50.