Comprehensive Guide to Cardiac Rhythms and Emergency Interventions

Vagal Maneuvers Overview: These techniques are designed to stimulate the vagus nerve to slow down the heart rate, particularly in cases of SVT (often referred to as SCT in specific contexts). * Common Techniques: * Bearing down (Valsalva maneuver). * Blowing through a straw or out of a syringe. * Placing the patient upside down or having them "chump" upside down. * Older/Historical techniques: Putting hands or face in cold water (the diving reflex). Note: This is not recommended currently due to the risk of aspiration. * Pediatric Variations: A specific practice mentioned by a cardiologist at Cooks involved grabbing a small child (e.g., a $2$ or $3$ year old) by the legs and holding them upside down to achieve the same vagal response. * The "IV Reflex": Sometimes just the act of starting an IV can convert a patient from SVT intentionally or unintentionally. The patient might prepare for the "poke" by gritting their teeth or bearing down, effectively performing a vagal maneuver that converts the rhythm on the monitor.
Clinical Workflow: Healthcare providers typically attempt these non-pharmacological interventions first because pharmacological options (like Denison) can cause significant pauses in heart rhythm that may distress the patient. * If a patient converts via a vagal maneuver, they typically stay in the Emergency Room for several hours for monitoring to ensure they do not revert to the tachycardia.

Rationale for EKGs: Electrocardiograms are performed to identify: * Arrhythmias. * Myocardial Infarctions (MIs). * Conduction problems. * Pre-surgical clearance for routine surgeries.
Target Populations: In the ER, approximately $70\%$ of patients receive an EKG, blood work, and an IV. Specific patients requiring cardiac monitoring include: * Anyone with chest pain. * Septic patients. * Major trauma victims. * Patients with a cardiac history. * Diabetic or renal patients (due to high risk for "crazy high" potassium levels).
Cardiac Anatomy and Waves: * SA Node and AV Node: The primary electrical centers where impulses travel to stimulate the ventricles. * P-wave: Represents atrial depolarization. * QRS Complex: Represents ventricular depolarization. * T-wave: Crucial for identifying ischemia or MIs (recovery process). * E-wave: Sometimes visible, but less common.

AFib Characteristics: * It is an "irregularly irregular" rhythm. * The EKG lack visible P-waves; the baseline appears jagged. * It is common in older age, post-MI, post-CABG (cardiac surgery), and in patients with sleep apnea.
Rapid Ventricular Response (RVR): * Occurs when the heart rate becomes uncontrolled and very fast (e.g., hopping between $110$ , $120$ , and $130\,\text{bpm}$ every few seconds). * Dangerous because the ventricles are not coordinated with the electrical activity. * Requires hospitalization and often a medication drip.
Long-term Management: * Patients with AFib must be on a blood thinner for the rest of their lives to prevent clots and strokes, even if their rate is controlled by medication. * AFib essentially never "gets better" or goes away; it is a chronic condition similar to hypertension. * Acute exacerbations can be triggered by sepsis or high fevers. * Ablation is a possible surgical intervention.

First-Degree/Wenckebach: Also known as Winky Buck. * The PR interval gradually prolongs until a QRS complex is dropped (blocked). * Usually asymptomatic; often seen with age or post-MI. * Atropine (an anticholinergic) may be used if the heart rate is low. * If the rate is significantly low, a temporary pacemaker may be required.
Mobitz II (Second-Degree Block): * Characterized by single P-waves and sudden dropped QRS complexes. * Treatment: Transcutaneous pacing (using pacer pads) and potentially a permanent pacemaker if bradycardia persists.
Third-Degree Block: * The most dangerous block. * Treatment: Transcutaneous pacemaker, Dopamine drip, or Epinephrine drip to increase heart rate and blood pressure.

PVCs (Premature Ventricular Contractions): Can be unifocal, multifocal, or occur as bigeminy.
Ventricular Tachycardia (VTAC): * Defined as a run of $3$ or more PVCs. * It is a monomorphic, regular rhythm where the ventricle takes over as the pacemaker. * Stable (With Pulse): Patient is conscious/stable-ish. Use medications (Amiodarone, Lidocaine, or Procainamide) and cardioversion. * Unstable (No Pulse): Immediate CPR and defibrillation (shock).
Ventricular Fibrillation (VFib): * The ventricle is quivering (looks like a "big scribble"). * There is zero cardiac output and no pulse. The patient is clinically dead. * Treatment: Start CPR immediately and defibrillate with high-dose electricity.
Pulseless Electrical Activity (PEA): * Electrical activity is present on the monitor (may even look like normal sinus), but there is no mechanical heart function (no pulse). * Commonly seen after a code or after defibrillation. * Treatment: CPR and Epinephrine pushes. PEA is not a shockable rhythm.
Asystole: * The "flatline." No electrical or mechanical activity. * Important: Contrary to "Grey's Anatomy," asystole is NOT a shockable rhythm. * Treatment: CPR and Epinephrine to stimulate some activity. The goal is perfusion to the brain and kidneys.

Pharmacology: * Denison (Adenosine): Requires a large-bore IV ( $18$ to $20\,\text{gauge}$ ) specifically in the AC (antecubital) vein. It must be pushed fast and flushed fast due to its extremely short half-life. * Atropine: Anticholinergic used for blocks/bradycardia. * Epinephrine: Used in pulseless scenarios (Asystole/PEA); pushed fast in emergency codes. * Magnesium: Potential IV medication for specific arrhythmias like Torsades.
Electricity: * Defibrillation: High-dose electricity for VFib or pulseless VTAC. * Cardioversion: Synchronized shock for unstable patients with a pulse. * Transcutaneous Pacing: Pacer pads used to regulate slow heart rates.
Code Dynamics: During a code, roles are specific. A recorder (nurse) documents start/stop times of CPR, pulse checks, and the timing of Epinephrine doses (typically every $3$ minutes per ACLS protocols).

Question: "What would those be? [Vagal maneuvers]"
Response: There are many. You can see them on YouTube by searching Denison, Bagel My Neighbors, or looking at techniques like dumping a person upside down or using a syringe to blow out.
Question: "Will I have to know all the boxes on the EKG?"
Response: Do not get "crazy" learning every box. Focus on identifying the rhythm and the treatment. There are typically around $5$ EKG strip questions on the $65$ -question exam.
Question: "What defines a patient as stable?"
Response: In critical care, "stable" means the patient has a pulse. If there is no pulse, low blood pressure, or they are unconscious, they are considered unstable and require more aggressive interventions like cardioversion or CPR.