Drug and Electrolyte Effects Flashcards
Inflammation of the pericardium
Pericarditis
What ECG changes do you see in pericarditis?
Elevated ST segments (usually flat or concave) that are more diffuse, affecting many leads (unlike more localized changes seen in MIs)
Depressed PR interval commonly seen as well
No Q waves
Characteristics of benign early repolarization on ECG
J-point notching
T-wave asymmetry, concordance with QRS
Upsloping ST-segment
No reciprocal ischemic findings in other leads
Stable findings on ECG
Minimal ST-elevation (relative to T-wave, <1/4 height)
In pericarditis with _______, fluid collection around the heart dampens the electrical output
Effusion
Characteristics of Pericarditis with effusion on ECG
Low voltage** seen in all leads with large effusions
May still see T wave and ST segment changes consistent with pericarditis
If large —> electrical alternans** manifested by changing amplitude of the QRS complex
Low voltage and electrical alternans
Pericarditis with effusion
Acute occlusion of the pulmonary artery that can cause acute right heart failure
Pulmonary embolism
May see evidence of distension of the right atrium and right ventricle
ECG changes seen with pulmonary embolisms
Most common = sinus tachycardia (esp if PE is small)
In massive PE —> S1-Q3-T3 pattern
What does S1-Q3-T3 mean?
Large S wave in Lead I
Deep Q wave in Lead III
Inverted T wave in Lead III
Indicative of massive PE
Other less common ECG changes you might see with PEs
RAD
Signs of RAE (tall, peaked P waves)
New RBBB acutely
T waves may be inverted in precordial leads (V1-4)
Persistence of lateral S-waves (even without complete RBBB)
TACHYARRHYTHMIAS
What is Long QT Syndrome (LQTS)?
Rare congenital condition
Delayed repolarization following depolarization, which is associated with ventricular dysrhythmias including ventricular fibrillation and Torsade de Pointes (TdP)
Arrhythmias often associated with exercise
What is Short QT Syndrome?
Rare inherited condition (QTI < 0.35s)
Syncope, ventricular arrhythmias, risk of sudden cardiac death
What is QTc Interval?
The “Corrected QT Interval”
Represents depolarization and repolarization but is corrected for heart rate
Can be determined from tables, software, or calculations
Visual tip for determining if QT interval is normal
Normal QT is less than half the R-R interval
There is an increased risk of Torsade de Pointes if QTc is prolonged - _______ in Men and ______ in Women
> 0.44s in Men
> 0.46s in Women
Key ECG characteristics for Hyperkalemia
Tall, peaked T waves
Flattened P waves
1st-degree AV heart block
Widened QRS complexes
Merging of S and T waves forming a sine-wave pattern
What’s the deal with the sine-wave pattern seen in hyperkalemia?
Widened QRS complexes and peaked T waves become indistinguishable, forming a sine-wave like pattern
Seen when K > 7.0 mmol/L
When do you start to see peaked narrow T waves in all leads?
When K 5.5-6.5 mmol/L
What are the key ECG characteristics for hypokalemia?
Flattening of the T waves
Appearance of prominent U waves
ST segment depression
Tall, peaked T waves and widened QRS complexes —> sine-wave pattern
Hyperkalemia
Flattening of the T wave and appearance of U waves
Hypokalemia
What happens to a patient’s heart in hypercalcemia?
Decreased automaticity with slowed conduction —> increased PR interval and QRS interval, possible BBBs and AV block
Shorter refractory period —> shorter ST segment and shorter QT interval
QT interval is _______ with hypercalcemia and ________ with hypocalcemia
Shortened = hypercalcemia
Prolonged = hypocalcemia
When might you see a prolonged QT interval?
Hypo K+
Hypo Ca2+
Hypo Mg2+
What might happen if prolonged QT is not corrected?
May progress to ventricular tachycardia or Torsade de Pointes
Digoxin affects the movement of _____ and _____ during depolarization and repolarization
Sodium and Calcium
Slows sodium movement into cell
Facilitates movement of calcium out of the cell
What are the end results of digoxin use?
Increased myocardial contractility and improved heart pumping ability
Slows HR and AV conduction
How is Digoxin used?
To treat fast atrial dysrhythmias (positive inotrope that slows HR and AV conduction)
What are the two categories of ECG changes with digoxin?
At therapeutic drug levels (0.8-2.0 ng/ml)
• Parasympathetic effect —> slowed HR
• See “Digoxin effect” on ECG - do not indicate need to d/c drug
Toxic blood levels (>2.4 ng/ml)
• Will see conduction blocks or tachy-dysrhythmias or both
• Increased risk with renal disease, hypokalemia, aging
There is an increased risk of toxicity with digoxin in patients with…
Renal disease
Hypokalemia
Aging
Digoxin effect changes
(See at therapeutic levels - don’t need to d/c)
Shortened QT interval (shorter with dig toxicity)
Flattened T waves
Asymmetric ST depression and T wave inversion in leads with tall R waves (gradual downslope of ST segment)
• Different from ST depression seen in ischemia)
Why are renal patients advised not to take digoxin?
Renally excreted and very narrow therapeutic margin —> extreme risk of toxicity
What ECG changes do you see with toxic levels of digoxin?
Slows conduction —> 1st, 2nd, or 3rd degree AV block
Causes virtually any tachydysrhythmia (a tachy, VT, VF)
PAT with 2nd-degree AV block (2:1) most characteristic
Toxicity can be exacerbated with hypokalemia
Drugs that can prolong QT interval, putting patients at risk for v tach and TdP
Anti-arrhythmias (quinidine, Procainamide, disopyramide, Amiodarone, Sotalol)
TCAs (Amitriptyline, doxepin, nortriptyline)
Phenothiazines (prochlorperazine)
Macrolides (Azithromycin, clarithromycin, erythromycin)
How should you monitor drug effects when prescribing drugs that can prolong QT?
Monitor QTI and d/c drug if >25% prolongation develops (QTc exceeds 0.5s)
What happens to the ECG in TCA overdose?
Prolongation of QT
Narrow QR portion with widened RS portion
Often with long PRI hidden beneath T
What happens to the ECG in hypothermia?
All intervals prolonged (PRI, QRS, QTI)
Osborn waves
What are Osborn waves?
Distinctive type of ST segment elevation w/ an abrupt ascent at the J-point then a plunge back to the baseline
Why do you often see muscle artifact on ECG with hypothermia?
Shivering. Duh.
Rare clinical syndrome due to an inherited autosomal dominant genetic defect —> ECG abnormalities which cause sudden death due to ventricular fibrillation or rapid v tach
Brugada Syndrome
Hx and Sx with Brugada Syndrome
FH of sudden cardiac death
PMH of serious heart rhythm problems and severe fainting spells
More common in younger patients (30’s)
More prevalent in Asian populations
Treatment for Brugada Syndrome
ICD (Implantable cardioverter-defibrillator)
Brugada Syndrome is characterized by _______ on ECG
3 different patterns with variable ST segment elevation abnormalities
