Cardiovascular Disorders: Dysrhythmias, Structural Diseases, and Coronary Syndromes

Comprehensive vocabulary flashcards covering cardiac electrophysiology, dysrhythmias, conduction blocks, pacemakers, ICDs, infectious/inflammatory heart diseases, valvular pathologies, cardiomyopathies, and coronary artery disease.

Automaticity

The intrinsic ability of cardiac tissue cells to initiate an electrical impulse spontaneously and continuously without external stimulation.

Excitability

The property of myocardial tissue that enables it to be electrically stimulated by an impulse.

Conductivity

The ability of cardiac cell membranes to transmit an electrical impulse in an orderly, sequential manner along the conduction pathway.

Contractility

The ability of myocardial muscle fibers to respond mechanically to an electrical impulse by shortening and producing a contraction.

Cardiac Action Potential

A 5-phase cycle ($\text{Phase } 0$ to $\text{Phase } 4$) driven by the movement of ions ($Na^+$, $Ca^{2+}$, and $K^+$) across the myocardial cell membrane, transitioning from rapid depolarization to resting potential.

Sinoatrial (SA) Node

The primary intrinsic pacemaker of the heart, located in the right atrium, which normally initiates impulses at a regular rate of $60 - 100\,\text{bpm}$.

P Wave

The first positive deflection on an ECG rhythm strip, representing electrical depolarization of the atria.

PR Interval

The ECG interval measuring the time required for an impulse to travel through the atria and undergo delay at the AV junction; normal duration is $0.12 - 0.20\,\text{seconds}$.

QRS Complex

The ECG waveform representing ventricular depolarization; normal duration is $0.04 - 0.12\,\text{seconds}$.

T Wave

The ECG waveform following the S wave that represents ventricular repolarization.

Einthoven's Triangle

An equilateral triangle diagram representing the standard bipolar limb leads (Lead I: RA to LA; Lead II: RA to LL; Lead III: LA to LL) using 3 electrodes to detect frontal-plane electrical vectors.

Normal Sinus Rhythm (NSR)

A regular cardiac rhythm originating from the SA node at a rate of $60 - 100\,\text{bpm}$, characterized by uniform P waves preceding every uniform QRS complex with consistent normal PR and QRS intervals.

Sinus Bradycardia

A regular rhythm originating in the SA node with a rate of $< 60\,\text{bpm}$, treated symptomatically with IV atropine or a pacemaker.

Sinus Tachycardia

A regular rhythm originating in the SA node with a rate of $> 100\,\text{bpm}$, driven by stress, fever, hypovolemia, or stimulants, and managed by treating the underlying cause, vagal maneuvers, or beta/calcium channel blockers.

Sinus Arrhythmia

A slightly irregular rhythm initiated by the SA node at a rate of $60 - 100\,\text{bpm}$, commonly varying with respiratory cycles due to changes in vagal tone; benign and common in youth.

Premature Atrial Contraction (PAC)

An early ectopic beat originating in atrial tissue outside the SA node, producing an abnormally shaped or distorted P wave, followed by an otherwise normal QRS complex.

Atrial Flutter

An atrial tachyarrhythmia characterized by recurring, regular, sawtooth-shaped flutter ("F") waves at an atrial rate of $240 - 360\,\text{bpm}$, typically with a fixed AV conduction ratio ($2:1$, $3:1$, or $4:1$).

Atrial Fibrillation

The most common cardiac arrhythmia, characterized by rapid, disorganized atrial twitching with an atrial rate of $350 - 600\,\text{bpm}$, no discernible P waves, an irregularly irregular ventricular response, and loss of the atrial kick ($\approx 30\%$ of cardiac output).

Synchronized Cardioversion

An elective or urgent electrical shock ($50 - 200\,\text{Joules}$) delivered by a defibrillator synchronized precisely to the R/S wave of the QRS complex in an awake, sedated patient.

Defibrillation

The emergency delivery of an unsynchronized direct current countershock ($200 - 360\,\text{Joules}$) through the myocardium to depolarize all cells simultaneously, indicated for pulseless Ventricular Tachycardia and Ventricular Fibrillation.

Supraventricular Tachycardia (SVT)

A narrow-complex tachycardia ($\text{QRS} < 0.12\,\text{seconds}$) originating above the bundle of His with a rapid, regular rate of $100 - 300\,\text{bpm}$, treated with vagal maneuvers, adenosine, or synchronized cardioversion.

Premature Ventricular Contraction (PVC)

An ectopic impulse originating within a ventricular focus that produces an early, wide, and bizarre QRS complex ($> 0.12\,\text{seconds}$) followed by a full compensatory pause and an inverted T wave.

Ventricular Tachycardia (VT)

A life-threatening dysrhythmia defined as a run of 3 or more consecutive PVCs with a rapid rate of $100 - 250\,\text{bpm}$ and wide, bizarre QRS complexes; can rapidly deteriorate into ventricular fibrillation.

Ventricular Fibrillation (VF)

A lethal, pulseless arrhythmia originating from chaotic ventricular foci with absent organized electrical complexes and no cardiac output, requiring immediate CPR and unsynchronized defibrillation.

Pulseless Electrical Activity (PEA)

A clinical condition where organized electrical activity is demonstrated on an ECG monitor, but no mechanical contraction or palpable pulse is generated; treated by CPR and addressing reversible "H's and T's".

Therapeutic Hypothermia

A post-cardiac arrest neuroprotective protocol that cools comatose patients to $32 - 34\,^\circ\text{C}$ for $12 - 48\,\text{hours}$ to lower cerebral metabolic demand and reduce intracranial pressure.

First-Degree AV Block

A benign conduction delay through the AV node characterized by a prolonged, constant PR interval greater than $0.20\,\text{seconds}$, with regular rhythm and a $1:1$ P-to-QRS ratio.

Second-Degree AV Block, Type I (Wenckebach)

A progressive conduction disturbance characterized by PR intervals that gradually lengthen cycle-by-cycle until a single P wave fails to conduct and its QRS is dropped, after which the cycle repeats.

Second-Degree AV Block, Type II (Mobitz II)

A conduction defect where nonconducted P waves occur intermittently without antecedent PR lengthening; conducted beats exhibit constant PR intervals, carrying high risk of progression to complete heart block.

Third-Degree AV Block (Complete Heart Block)

Complete absence of electrical conduction between atria and ventricles, resulting in independent atrial and ventricular pacing (AV dissociation) where P waves and QRS complexes beat regularly but completely independently.

Bundle Branch Block (BBB)

Interrupted or delayed conduction through either the right or left bundle branch, causing asynchronous ventricular depolarization and a widened QRS complex exceeding $0.12\,\text{seconds}$.

Transcutaneous Pacing

An emergency, temporary method of cardiac pacing where electrical current is delivered through the chest wall musculature via two large cutaneous electrode patches.

Transvenous Pacing

A temporary or permanent pacing method where lead wires are threaded through a central vein (subclavian, jugular, or cephalic) and lodged into the right atrium, right ventricle, or both.

Epicardial Pacing

A temporary pacing method where wires are affixed directly to the epicardium during open-heart surgery, exit through the chest wall, and attach to an external generator if post-operative pacing is needed.

Pacer Spike

A sharp, narrow vertical deflection on the ECG monitor signifying that the pacemaker generator has delivered an electrical stimulus to the myocardium.

Failure to Sense

A pacemaker malfunction where the generator fails to recognize the patient's intrinsic cardiac activity, causing it to fire impulses inappropriately or too early on the ECG strip.

Failure to Capture

A pacemaker malfunction where the emitted electrical stimulus (pacer spike) fails to depolarize the myocardium, visible as a pacer spike not followed by a P wave or QRS complex.

Failure to Pace

A pacemaker failure where the pulse generator fails to deliver an electrical impulse when expected, resulting in an absence of pacing spikes where they should be present.

Runaway Pacemaker

A dangerous pacemaker malfunction characterized by rapid, uncontrolled firing of the pulse generator above its set rate limit due to battery or circuit malfunction.

Twiddler Syndrome

A complication where a patient intentionally or inadvertently manipulates and rotates the pulse generator within its subcutaneous pocket, leading to lead displacement and pacing failure.

Implantable Cardioverter Defibrillator (ICD)

An implanted electronic device that continuously monitors cardiac rhythm, detects lethal tachyarrhythmias (VT/VF), and delivers antitachycardia pacing or high-voltage countershocks to terminate the arrhythmia.

Sudden Cardiac Death (SCD)

Unexpected, abrupt death occurring within $1\,\text{hour}$ of symptom onset, most frequently caused by ventricular fibrillation triggered by underlying coronary artery disease.

Rheumatic Heart Disease (RHD)

A chronic cardiac condition resulting from single or repeated episodes of rheumatic fever following group A beta-hemolytic streptococcal pharyngitis, characterized by valvular stenosis or regurgitation.

Aschoff Bodies

Pathognomonic localized nodules of chronic inflammatory tissue that form within the myocardium and cardiac tissues during active rheumatic carditis.

Infective Endocarditis

An infection of the endothelial layer of the heart and valves caused by bacteria or fungi, resulting in vegetative lesions, valve damage, and systemic embolization.

Vegetations (Infective Endocarditis)

Friable, infectious clusters of fibrin, leukocytes, platelets, and microbes that adhere to cardiac valves and endocardial surfaces, prone to fracturing and embolizing to distant organs.

Myocarditis

Inflammation of the heart muscle (myocardium) triggered by viral, bacterial, or autoimmune processes; treated cautiously with heart failure drugs because digitalis sensitivity may be heightened.

Pericarditis

Inflammation of the parietal and visceral pericardial layers causing sharp retrosternal chest pain worsened by deep inspiration and lying flat, typically relieved by sitting forward.

Pericardial Friction Rub

A harsh, grating, or creaking auscultatory sound produced by rubbing between inflamed pericardial surfaces, heard best with the diaphragm along the lower left sternal border with the patient leaning forward.

Cardiac Tamponade

Life-threatening compression of the heart caused by excessive fluid or blood accumulation within the pericardial sac, which impairs diastolic filling and causes a severe drop in cardiac output.

Constrictive Pericarditis

A chronic condition characterized by fibrous thickening, scarring, and calcification of the pericardium that encases the heart in a rigid shell, severely restricting diastolic expansion.

Valvular Stenosis

A pathological narrowing and stiffening of a heart valve orifice that obstructs forward blood flow and increases the pressure workload of the pumping chamber behind it.

Valvular Regurgitation (Insufficiency)

Incomplete closure of cardiac valve leaflets allowing backward leakage of blood into the preceding chamber during systole or diastole, resulting in volume overload.

Mitral Valve Prolapse (MVP)

A structural disorder, twice as prevalent in women, in which one or both mitral valve leaflets balloon upward into the left atrium during ventricular systole, often producing a midsystolic click and late systolic murmur.

Mitral Regurgitation (MR)

Backflow of blood from the left ventricle into the left atrium during systole, characterized by a loud, high-pitched holosystolic blowing murmur heard best at the cardiac apex that radiates to the left axilla.

Mitral Stenosis (MS)

Narrowing and fibrotic fusion of the mitral valve opening that impedes blood flow from the left atrium into the left ventricle during diastole, predominantly caused by rheumatic endocarditis.

Aortic Regurgitation (AR)

The retrograde leakage of blood from the aorta back into the left ventricle during diastole due to incompetent aortic valve leaflets, producing volume overload and LV dilation.

Corrigan's Pulse

A physical exam finding characteristic of aortic regurgitation consisting of a bounding, forceful pulse that rapidly collapses (water-hammer pulse) due to widened pulse pressure.

Aortic Stenosis (AS)

Progressive narrowing of the aortic valve orifice—commonly from degenerative calcification in patients $> 60\,\text{years}$ old—characterized by a loud, harsh crescendo-decrescendo systolic murmur over the aortic area.

Percutaneous Balloon Valvotomy

A minimally invasive catheterization procedure wherein a balloon catheter is advanced across a stenosed valve and inflated to crack open fused commissures and enlarge the orifice.

Dilated Cardiomyopathy (DCM)

The most common form of cardiomyopathy, defined by marked dilation of both ventricular cavities with reduced wall thickness, impaired systolic contraction, and severely reduced ejection fraction.

Restrictive Cardiomyopathy (RCM)

A rare myocardial disorder characterized by excessively rigid, non-compliant ventricular walls that severely limit diastolic filling despite relatively normal myocardial thickness and systolic function, frequently associated with amyloidosis.

Hypertrophic Cardiomyopathy (HCM)

An autosomal dominant disorder characterized by disproportionate, asymmetric hypertrophy of the ventricular myocardium and septum, leading to impaired diastolic relaxation and sudden cardiac death in young athletes.

Alcohol Septal Ablation

A percutaneous therapeutic procedure for obstructive hypertrophic cardiomyopathy in which absolute ethanol is injected into a septal coronary branch to produce a localized infarction and thin the obstructing septum.

Atherosclerosis

A progressive inflammatory process characterized by the abnormal accumulation of lipid deposits, inflammatory cells, and fibrous plaques within the arterial intima and wall.

Coronary Artery Disease (CAD)

The most prevalent cardiovascular disease in adults, caused by atherosclerotic narrowing or occlusion of the coronary arteries, resulting in diminished myocardial perfusion.

Metabolic Syndrome

A constellation of major cardiovascular risk factors including visceral obesity, insulin resistance, hypertension, elevated serum triglycerides, and reduced HDL-cholesterol.

Angina Pectoris

A clinical syndrome characterized by paroxysmal episodes of substernal chest discomfort or pressure caused by transient myocardial ischemia when cardiac oxygen demand exceeds coronary blood supply.

Unstable Angina

An acute presentation of coronary ischemia characterized by chest discomfort that increases in frequency, duration, or severity, often occurring at rest and not fully relieved by rest or sublingual nitroglycerin.

Nitroglycerin (NTG)

A potent nitrate vasodilator administered sublingually every $5\,\text{minutes}$ up to 3 doses to relieve acute anginal attacks by decreasing preload, afterload, and myocardial oxygen demand; side effects include hypotension and headache.

Acute Coronary Syndrome (ACS)

An emergent continuum of clinical conditions caused by acute plaque rupture and sudden coronary occlusion, encompassing unstable angina, non-ST elevation MI (NSTEMI), and ST-elevation MI (STEMI).

Myocardial Infarction (MI)

Irreversible cellular death and necrosis of myocardial tissue resulting from prolonged, severe ischemia; hallmark diagnostic findings include persistent chest pain, ST-segment elevation across contiguous leads, and elevated cardiac biomarkers.

Cardiac Troponin

A highly specific and sensitive regulatory protein released into the bloodstream following myocardial necrosis, recognized as the premier biomarker for confirming acute myocardial infarction.

Percutaneous Transluminal Coronary Angioplasty (PTCA)

A catheter-based percutaneous intervention in which a balloon-tipped catheter is introduced (via radial or femoral artery) to compress atheromatous plaque, followed by stent deployment.

Coronary Artery Bypass Graft (CABG)

A surgical revascularization procedure in which an autologous vascular conduit—such as the greater saphenous vein or internal mammary artery—is grafted to bypass stenosed coronary arteries.

Cardiopulmonary Bypass (CPB)

A mechanical extracorporeal circulatory circuit that temporarily takes over the oxygenating and pumping functions of the heart and lungs, providing a bloodless, motionless surgical field during open-heart surgery.