Cardio - Syncope and Miscellaneous Study Guide

Syncope: Overview and Definitions

• Syncope

  • Defined as a transient, self-limited loss of consciousness (TLOC).

  • The underlying mechanism is acute global cerebral hypoperfusion.

  • Characterized by a rapid onset.

  • Recovery is spontaneous and complete, requiring no medical intervention to restore consciousness.

• Pre-syncope

  • Refers to the state where a patient experiences the prodromal symptoms of syncope without actually losing consciousness.

  • Clinical symptoms include:

    • Lightheadedness.

    • Faintness.

    • Weakness.

    • Fatigue.

    • Visual disturbances (e.g., blurring, tunneling).

    • Auditory disturbances.

    • Sweating (diaphoresis).

Neurally Mediated Syncope (NMS)

• General Concept

  • Involves a transient change in the reflexes responsible for maintaining cardiovascular homeostasis.

  • Results in a temporary failure of blood pressure ($BP$) control.

  • It is the most common ($MC$) type of syncope.

• Vasovagal Syncope

  • Commonly referred to as the "common faint."

  • Often provoked by specific triggers such as:

    • Pain.

    • The sight of blood.

    • Exposure to needles.

    • Extreme emotional distress.

• Situational Syncope

  • Triggered by specific, localized stimuli that provoke reflex vasodilation and bradycardia.

  • Common situations include:

    • Violent coughing.

    • Micturition (urination).

    • Defecation.

    • Laughing.

    • Swallowing.

• Carotid Sinus Hypersensitivity

  • Triggered by mechanical stimulation of the carotid sinus.

  • Common triggers include:

    • Neck movement.

    • Shaving.

    • Wearing tight neckties.

    • Other activities that exert pressure upon the carotid sinus.

  • This condition is more common in elderly populations.

• Management of Recurrent/Refractory Syncope

  • Pharmacological options for patients who do not respond to basic measures include:

    • Midodrine.

    • Fludrocortisone.

Orthostatic Hypotension (OH)

• Diagnostic Criteria

  • A reduction in systolic blood pressure ($SBP$) of over $20\,mmHg$ or a reduction in diastolic blood pressure ($DBP$) of over $10\,mmHg$ occurring within $3\,minutes$ of standing.

• Pathophysiology

  • Characterized by a failure of sympathetic vasoconstriction.

  • A hallmark sign is the lack of a compensatory heart rate ($HR$) increase upon standing.

• Neurogenic Orthostatic Hypotension

  • Caused by autonomic dysfunction affecting multiple organ systems.

  • Associated conditions include:

    • Shy-Drager syndrome.

    • Parkinson's disease.

    • Dementia with Lewy bodies.

    • Peripheral neuropathies.

    • Spinal cord issues.

    • Brain stem lesions.

    • Cerebrovascular accident ($CVA$).

    • Multiple sclerosis.

• Iatrogenic Orthostatic Hypotension

  • Caused by medications that interfere with blood pressure regulation, including:

    • Antihypertensives.

    • Adrenoreceptor blockers.

    • Nitrates.

    • Tricyclic antidepressants ($TCA$).

    • Dopamine receptor agonists.

    • Erectile dysfunction ($ED$) drugs.

    • Diuretics.

Cardiogenic Syncope and Related Conditions

• Cardiogenic Syncope

  • Syncope resulting from an arrhythmia or structural heart disease.

  • This type is associated with the highest likelihood of a bad clinical outcome.

  • Potential causes include:

    • Bradyarrhythmias.

    • Ventricular tachyarrhythmias.

    • Long QT syndrome.

    • Brugada syndrome.

    • Valvular heart disease.

    • Ischemic heart disease.

    • Cardiomyopathy.

    • Cardiac masses (e.g., tumors).

    • Pericardial effusion.

• Cataplexy

  • Characterized by a sudden loss of muscular tone while consciousness is maintained.

  • Typically occurs following a strong emotional stimulus.

Cardiac Tumors

• Myxoma

  • Most common ($MC$) primary cardiac tumor in adults.

  • Primarily benign.

  • Location: More often found on the left side of the heart.

  • Clinical markers: May present with a murmur or a characteristic "tumor plop" on auscultation.

  • Treatment: Surgical excision.

• Papillary Fibroelastoma

  • Second most common primary cardiac tumor.

  • Approximately $80\%$ are found on heart valves.

  • Diagnostic feature: Multiple hair-long fronds of tumor observed.

• Malignant Tumors

  • Sarcoma: Represents the majority of primary malignant cardiac tumors.

  • Metastatic Tumors: The most common ($MC$) type of malignant cardiac tumor overall.

• Diagnostic Tools for Cardiac Tumors

  • Echocardiogram ($ECHO$).

  • Magnetic Resonance Imaging ($MRI$).

Cardiovascular Health in Diabetes

• Coronary Heart Disease (CHD)

  • The leading cause of death in patients with Type 2 Diabetes Mellitus ($T2DM$).

• Pharmacological CV Protection

  • Diabetes medications that offer cardiovascular benefits include:

    • Sodium-glucose cotransporter-2 inhibitors ($SGLT2i$).

    • Glucagon-like peptide-1 ($GLP\text{-}1$) agonists.

Pulmonary Embolism (PE)

• Definition and Presentation

  • A blood clot located in the lungs.

  • Clinical symptoms and signs include:

    • Dyspnea (shortness of breath).

    • Cough.

    • Hemoptysis (coughing up blood).

    • Tachypnea (rapid breathing).

    • Rales.

    • Tachycardia (rapid heart rate).

• Diagnostic Pathway

  • Computed Tomography Angiography (CTA): Considered the first-line diagnostic tool if PE is suspected.

  • Pulmonary Angiogram: The gold standard diagnostic for PE, though it is invasive.

  • VQ Scan: An alternative diagnostic if the patient is unable to undergo a CT scan (e.g., due to renal failure or dye allergy).

• Risk Stratification and Screening

  • Wells Criteria: A tool used to objectify the clinical risk for PE.

  • PERC Rule: Used to rule out PE if the result is completely negative.

  • D-dimer: A laboratory test used to rule out PE specifically in cases of low or intermediate clinical suspicion.

• Treatment and Interventions

  • Anticoagulation therapy: Typically consists of Heparin plus Warfarin, or Direct Oral Anticoagulants ($DOAC$).

  • Inferior Vena Cava (IVC) Filter: Indicated if anticoagulation is contraindicated or if PE recurs despite therapy.

  • Thrombectomy: A last-resort treatment for large proximal PE in patients who are hemodynamically unstable.

Sports Cardiology

• Hypertrophic Cardiomyopathy (HCM)

  • The most common cause ($MCC$) of sudden cardiac death in athletes.

• Athlete’s Heart

  • Non-pathologic compensatory changes in the heart designed to increase cardiac output ($CO$) due to physical demand.

  • Characteristics include:

    • Biventricular hypertrophy (noted as mild if the wall thickness is less than $15\,mm$).

    • Mild-to-moderately dilated left ventricle ($LV$).

    • Maintained diastolic function (unlike pathologic conditions).