3. Palpitations, syncope, sudden death

Understanding Palpitations

Palpitations are the sensations of having a rapid, fluttering, or pounding heart. These sensations are not only uncomfortable but can also be alarming. While palpitations are often benign, they can occasionally signal a more serious condition. The key challenge in diagnosing palpitations lies in their transient nature, as they often resolve before medical evaluation.

Common Causes

• Tachyarrhythmias: This is the most common direct cardiac cause of palpitations. These are conditions where the heart beats abnormally fast due to issues in the electrical impulses that regulate the heartbeat.

• Bradyarrhythmias: While less common, slow heart rates can sometimes cause palpitations, especially when they lead to significant reductions in cardiac output, manifesting as fatigue or syncope.

Risk Factors

• Stimulant Medication: Use of drugs such as caffeine, nicotine, or certain medications like decongestants and some psychiatric drugs can trigger palpitations.

• Emotional Stress: Anxiety, stress, and emotional disorders can provoke palpitations through sympathetic nervous system activation.

• Sepsis: This severe infection can affect heart rate and rhythm, leading to palpitations among other systemic symptoms.

• Anemia: Low hemoglobin levels can cause the heart to work harder to deliver oxygen to tissues, sometimes resulting in palpitations.

• Endocrine Disorders: Conditions like hyperthyroidism significantly increase metabolism and cardiac output, often leading to palpitations.

• Underlying Cardiac Disorders: Structural abnormalities such as valve defects, congenital heart disease, or the presence of additional conductive pathways (e.g., Wolff-Parkinson-White syndrome) can be underlying causes.

Diagnostic Approach

Due to the episodic nature of palpitations, capturing them during an episode can be challenging. The following are commonly used diagnostic tools and techniques:

• Patient History: Detailed discussion about the nature of the palpitations, their onset, duration, associated symptoms, and potential triggers.

• Physical Examination: To identify any signs of cardiac or systemic disease.

• Electrocardiogram (ECG): Although often normal if the patient is not experiencing palpitations during the test, it can reveal underlying rhythm abnormalities.

• Holter Monitor: A portable device worn for 24-48 hours to record the heart's electrical activity over a longer period.

• Event Monitors: For intermittent palpitations, an event monitor can be used for weeks to capture arrhythmias.

• Blood Tests: To check for anemia, thyroid dysfunction, and other possible metabolic causes.

• Echocardiogram: To evaluate heart structure and function, particularly if structural heart disease is suspected.

Causes of Palpitations

1. Sinus Tachycardia

Sinus tachycardia is a normal increase in heart rate that occurs in response to certain situations or conditions, which may cause palpitations:

• Stimulant Intoxication: Substances like cocaine, caffeine, and certain medications increase heart rate through sympathetic nervous system stimulation.

• Withdrawal from Substances: Alcohol, benzodiazepines, and beta-blockers can lead to increased heart rate during withdrawal as the body reacts to the absence of the previously inhibiting substance.

• Hypoglycemia: Low blood sugar can trigger a release of adrenaline, increasing heart rate.

• Hyperthyroidism: Excess thyroid hormone increases overall metabolism and cardiac output, often leading to higher heart rates and increasing the risk of atrial fibrillation.

• Pheochromocytoma: A rare tumor that can secrete excess catecholamines, thus increasing heart rate.

• Anxiety: A very common cause where the perception of a fast-beating heart can be both a symptom and cause of further anxiety.

• Autonomic Dysregulation: Conditions like POTS and inappropriate sinus tachycardia can cause increased heart rate upon standing or without significant physical exertion, particularly affecting young females.

2. Tachyarrhythmias

These are conditions where the heart rhythm is abnormally fast:

• Atrial Fibrillation: Irregular and often rapid heart rate originating from abnormal electrical impulses in the atria.

• Atrial Flutter: Similar to atrial fibrillation but with more organized electrical abnormalities.

• Supraventricular Tachycardia: Includes AVNRT and AVRT, which involve re-entry circuits typically in or near the AV node.

• Ventricular Tachycardia: A potentially life-threatening condition where the lower chambers of the heart beat very quickly, can occur due to myocardial infarction, ischemia, cardiomyopathy, or genetic conditions like long QT syndrome.

3. Bradyarrhythmias

Although less common, slow heart rhythms can still cause palpitations, especially when the reduced heart rate leads to insufficient blood flow:

• Slow Atrial Fibrillation with High-Degree AV Block: A unique scenario where the atria beat irregularly and quickly but few impulses pass to the ventricles.

• Complete Heart Block: There is a complete disconnect between the atrial and ventricular contractions, causing ineffective and unsynchronized heartbeats.

4. Premature Beats

These are extra beats that disrupt the regular rhythm of the heart and can be felt as a skipped beat followed by a stronger-than-normal contraction:

• Premature Atrial Contractions (PACs): Occur in the atria and are typically less symptomatic.

• Premature Ventricular Contractions (PVCs): Occur in the ventricles and can be more noticeable due to the compensatory pause that follows, leading to a stronger subsequent contraction.

ASSESMENT OF PALPITATIONS

1. History

Taking a detailed medical history is crucial in the evaluation of palpitations and can often provide key insights into the potential causes:

• Duration and Timing: Helps distinguish between transient, sporadic episodes and persistent conditions.

• Specific Triggers: Identifying activities, foods, or situations that provoke palpitations can indicate specific causes such as anxiety, dietary factors, or exercise-induced arrhythmias.

• Medication and Substance Use: Certain medications, caffeine, alcohol, and illicit drugs can all be relevant.

• Quality of Palpitations: Describing them as too fast, strong, or irregular helps differentiate the type of arrhythmia.

• Associated Symptoms: The presence of symptoms such as dyspnea, syncope, or chest pain can suggest more serious cardiac conditions.

• Other Health Conditions and Stressors: Underlying diseases or emotional stress can be contributing factors.

2. Physical Exam

• Vitals: Checking for any abnormalities in blood pressure, heart rate, and respiratory rate.

• Cardiac Exam: Includes palpating the chest for heaves or thrills, auscultating for any abnormal heart sounds or murmurs, and assessing jugular venous pressure to evaluate for signs of heart failure.

• Auscultation: Critical for detecting irregular heartbeats, murmurs which might indicate valve disorders, or other abnormalities.

• Thyroid Exam: An enlarged thyroid or signs of hyperthyroidism can be linked to palpitations.

3. Blood Tests

• Thyroid Function Tests: Hyperthyroidism is a common endocrine cause of palpitations.

• Drug Levels: Especially relevant if the patient is on medications known to affect heart rhythm or if there is suspicion of substance abuse.

4. Urine Test

• Drug Screening: Useful for identifying the presence of stimulants or other illicit substances that can cause palpitations.

5. Electrocardiogram (ECG)

• Routine ECG: Captures a snapshot of the heart's electrical activity and can identify arrhythmias, even if the patient is not currently experiencing palpitations.

• Extended Monitoring: A Holter monitor or event recorder can track the heart’s rhythm over 24 hours or longer, useful for detecting intermittent arrhythmias.

6. Echocardiogram

• Structural Assessment: Checks for heart disease that could cause palpitations, such as valve abnormalities, heart muscle issues, or other structural changes.

Advanced Diagnostic Tools

If initial tests do not conclusively determine the cause of palpitations, more specialized tests might be considered:

• Stress Test: To observe the heart's activity under physical stress.

• Electrophysiological Study: Invasive test to map the heart's electrical system, which can be helpful for complex arrhythmias not diagnosed by other means.

Typical Cases of Palpitations

1. Extrasystolic

   • Description: Characterized by the feeling of a skipped beat followed by a stronger-than-normal subsequent beat.

   • Characteristics: These palpitations are typically irregular and occur without any specific trigger. They are often due to premature atrial or ventricular contractions.

   • Patient Experience: The sensation of a skipped beat can be startling but is usually benign.

2. Tachycardiac

   • Description: This involves a significantly accelerated heart rate that can be regular or irregular.

   • Triggers: Often triggered by physical exertion, emotional stress, or could be idiopathic.

   • Associated Symptoms: May include syncope, dyspnea, fatigue, and chest pain, indicating more severe underlying conditions like arrhythmias that may need urgent evaluation.

3. Anxiety-Induced

   • Description: Generally a slight acceleration of heart rate, often with a gradual onset linked to stress or anxiety disorders.

   • Characteristics: Can be accompanied by non-cardiac symptoms like tingling in the hands, a lump in the throat, frequent sighing, and shortness of breath.

   • Patient Experience: These palpitations are typically more related to psychological factors and respond well to stress management and anxiety-reducing techniques.

4. Pulsation

   • Description: Describes a sensation of a pounding heart that maintains a normal rhythm.

   • Triggers: Usually occurs during or after physical effort or in emotional situations.

   • Characteristics: Although the heartbeat remains regular, the enhanced awareness of heartbeat can cause discomfort or concern.

Complications of Palpitations

1. Fainting (Syncope)

   • Occurs when the rapid heartbeat leads to insufficient blood flow and oxygen to the brain.

   • Rapid arrhythmias can drop blood pressure, causing transient loss of consciousness.

2. Cardiac Arrest

   • Life-threatening arrhythmias like ventricular fibrillation or sustained ventricular tachycardia may degenerate into cardiac arrest.

3. Stroke

   • Conditions such as atrial fibrillation can cause the heart to beat irregularly and inefficiently, leading to the formation of blood clots that can travel to the brain, causing a stroke.

4. Heart Failure

   • Persistent or chronic tachycardia can overwork the heart, leading to heart muscle fatigue and eventual heart failure where the heart can't pump blood effectively.

Causes of Syncope:

1. Cardiac Syncope

   • Description: This form of syncope occurs when the heart is unable to meet the body's oxygen demand, critically lowering cerebral perfusion. It is particularly concerning because of its association with high mortality.

   • Arrhythmogenic Subtype: Involves arrhythmias that either speed up or slow down the heart rate excessively, affecting cardiac output. Common conditions include sick sinus syndrome, AV block, supraventricular arrhythmias, ventricular tachycardia, and Torsades de pointes.

   • Cardiovascular Subtype: Involves structural problems that cause outflow obstruction, such as massive myocardial infarction (MI), aortic stenosis, pulmonary embolism, severe asymmetric septal hypertrophy, and cardiac tamponade.

2. Reflex Syncope

   • Also known as neurally mediated syncope, this is the most common type and involves an overreaction of the body’s reflexes that lead to sudden vasodilation and/or slowed heart rate, resulting in transient hypotension.

   • Subtypes:

     • Vasovagal Syncope: Triggered by factors like prolonged standing, emotional stress, or pain, and is most common in younger individuals.

     • Situational Syncope: Occurs during specific activities that increase intrathoracic pressure, such as coughing, sneezing, micturition (urination), or defecation, leading to peripheral vasodilation and reduced cerebral perfusion.

     • Carotid Sinus Syndrome: Triggered by increased sensitivity of the carotid sinus (located in the neck), which can cause significant drops in blood pressure when the neck area is manipulated or pressed.

3. Orthostatic syncope

Orthostatic syncope is a specific type of fainting that occurs upon standing up, attributed to inadequate autonomic nervous system response to maintain blood pressure and cerebral perfusion. This can manifest in several forms, each associated with different underlying mechanisms and requiring distinct approaches for management.

Subtypes of Orthostatic Syncope:

1. Sympathotonic Orthostatic Hypotension

   • Description: There is a decrease in systolic blood pressure upon standing, but with compensatory tachycardia (increased heart rate).

   • Causes: Commonly due to hypovolemia (low blood volume), the effects of certain medications, or prolonged bed rest which diminishes the body’s ability to regulate blood pressure.

   • Symptoms: May include dizziness, blurred vision, or fainting shortly after standing.

2. Asympathotonic Orthostatic Hypotension

   • Description: Characterized by a drop in systolic blood pressure upon standing without a compensatory increase in heart rate.

   • Causes: Often seen in conditions affecting the autonomic nervous system, such as diabetic neuropathy or Parkinson’s disease, where the normal heart rate response is impaired.

   • Symptoms: Similar to sympathotonic orthostatic hypotension but may be more severe due to the lack of heart rate compensation.

3. Postural Tachycardia Syndrome (PoTS)

   • Description: Marked by a significant increase in heart rate within ten minutes of standing. Unlike the other types of orthostatic hypotension, PoTS does not necessarily involve a significant drop in blood pressure.

   • Symptoms: Can include severe palpitations, dizziness, and lightheadedness upon standing.

Clinical Features of Syncope:

• Prodrome (Presyncope): Many types of syncope, especially vasovagal and orthostatic, may be preceded by warning signs such as dizziness, blurred vision, or nausea.

• Vasovagal Syncope: Often includes symptoms like decreased vision and hearing, nausea, pallor, feeling of warmth, lightheadedness, diaphoresis, and sometimes hyperventilation.

• Orthostatic Syncope: Typically presents with lightheadedness, nausea, and dizziness immediately after standing, reflecting the body's struggle to adapt to gravitational changes.

• Cardiac Syncope: Usually lacks a prodrome, leading to a sudden fall. This suddenness makes it particularly dangerous, especially for older adults, as there is little to no time to mitigate the fall.

• Convulsive Syncope: Characterized by brief, myoclonic jerks that can occur with loss of consciousness. It's important to distinguish these from true epileptic seizures, which are longer in duration and have different recovery characteristics.

DIAGNOSTICS OF SYNCOPE

1. Patient History

• Purpose: To gather essential clues about the potential causes of syncope.

• Key Aspects: Duration of unconsciousness (syncope is usually brief, less than 5 minutes), triggers (e.g., standing up, pain, emotional distress), behavior during the event (such as any movements that may suggest a seizure), use of medications, and any relevant medical or family history of cardiac or neurological conditions.

2. Electrocardiogram (ECG)

• Purpose: To identify any cardiac arrhythmias or structural abnormalities that could cause syncope.

• Application: An ECG is crucial for detecting conditions such as atrial fibrillation, ventricular tachycardia, or signs of previous myocardial infarction.

3. Blood Tests

• Tests Include: Complete blood count to assess for anemia; electrolyte panel to detect imbalances that might cause arrhythmias; creatinine levels to evaluate kidney function, which affects electrolyte balance; and urinalysis as part of a broader metabolic assessment.

• Rationale: To rule out metabolic causes of syncope such as severe dehydration or electrolyte imbalances.

4. Cardiac Origin Evaluation

• ECG Monitoring: Extended monitoring, such as with a Holter monitor or event recorder, can capture transient arrhythmic events that were not detected during the initial ECG.

• Stress ECG: To identify ischemic changes that occur during physical exertion.

• Echocardiography: To visualize the heart's structure and function, helping to diagnose issues like valve diseases, cardiac chamber sizes, and wall motion abnormalities.

• Cardiac Enzymes: To detect recent myocardial damage.

• Carotid Ultrasound with Doppler: To assess carotid artery patency and blood flow, particularly in older patients or those with risk factors for cerebrovascular disease.

5. Imaging

• Chest X-ray: Useful in detecting pulmonary causes of syncope such as a pulmonary embolism or severe pneumonia.

• CT/MRI: Indicated if there is a suspicion of neurological causes behind the syncopal episodes, such as brain tumors, stroke, or intracranial hemorrhages.

6. Orthostatic Hypotension Test

• Procedure: After lying flat for at least 5 minutes, the patient stands up while blood pressure and heart rate are measured repeatedly over several minutes.

• Criteria for Diagnosis: A drop in systolic blood pressure of more than 20 mmHg or diastolic blood pressure of more than 10 mmHg upon standing, or systolic blood pressure falling below 90 mmHg, indicates orthostatic hypotension.

7. Tilt Table Test

• Purpose: To diagnose different types of autonomic nervous system failures or sensitivities that lead to syncope.

• Procedure: The patient is secured on a table that then tilts them from a horizontal to a 70-degree upright position to mimic standing up, monitoring blood pressure and heart rate.

• Interpretation: Presence of reflex hypotension and bradycardia typically suggests vasovagal syncope; slow progressive hypotension without significant changes in heart rate points towards orthostatic intolerance.

Differential Diagnosis of Syncope

1. Seizure

   • Distinguishing Features: Presence of convulsive movements, tongue biting, and postictal confusion; bladder or bowel incontinence may also occur.

   • Evaluation: EEG can help differentiate seizure from syncope.

2. Subclavian Steal Syndrome

   • Description: Syncope or presyncope that occurs when using the arm on the side of a stenosed subclavian artery, which diverts blood away from the brain.

   • Diagnostic Tools: Doppler ultrasound and angiography to confirm the diagnosis.

3. Vertebrobasilar Insufficiency

   • Symptoms: Can include drop attacks, dizziness, visual disturbances, and bilateral sensory disturbances.

   • Evaluation: Imaging studies such as MRI/MRA of the neck and brain to assess blood flow in the vertebral and basilar arteries.

4. Hypoglycemia

   • Symptoms: Typical autonomic symptoms include restlessness, sweating, tremors, and pale skin, often occurring before loss of consciousness.

   • Diagnostic: Measurement of blood glucose levels.

5. Craniocerebral Injury

   • History: A recent head trauma followed by episodes of fainting or unconsciousness should raise suspicion.

   • Imaging: CT or MRI of the head to rule out structural brain injuries.

6. Heatstroke

   • Context: Exposure to a high-temperature environment with symptoms of central nervous system dysfunction such as confusion, agitation, and possible syncope.

   • Management: Rapid cooling and hydration are critical.

7. Hyperventilation Syndrome

   • Triggers: Often occurs in anxiety or panic disorders, leading to excessive breathing and subsequent reduction in blood carbon dioxide levels.

   • Symptoms: Dizziness, tingling in extremities, and sometimes syncope.

8. Cryptogenic Drop Attacks

   • Description: Sudden falls without loss of consciousness, primarily in elderly individuals, often without an identifiable cause.

   • Evaluation: Thorough investigation to exclude neurological causes.

Treatment of Syncope

1. Arrhythmogenic Syncope

   • Management: Antiarrhythmic medications or implantation of a pacemaker or defibrillator depending on the type of arrhythmia.

2. Carotid Sinus Syndrome

   • Preventive Measures: Avoidance of tight collars and ensuring adequate hydration.

   • Management: In some cases, pacemaker insertion might be necessary if significant bradycardia is documented.

3. Vasovagal Syncope

   • Behavioral Adjustments: Avoidance of known triggers, use of physical counterpressure maneuvers (e.g., leg crossing, muscle tensing).

   • Positional Strategies: Lying down with elevated legs can help abort or alleviate episodes.

4. Orthostatic Syncope

   • Lifestyle Modifications: Increased salt and fluid intake to boost blood volume.

   • Physical Support: Use of compression stockings to improve venous return.

   • Medication Review: Adjusting or discontinuing medications that may contribute to hypotension.

SUDDEN DEATH

Sudden cardiac death (SCD) is a severe and alarming event, typically resulting from cardiac causes that lead to an abrupt cessation of heart function. It's crucial to understand the potential causes and risk factors to better manage and potentially prevent these catastrophic events. Here’s a detailed look at the causes of SCD and their underlying mechanisms:

Common Causes of Sudden Cardiac Death

1. Ventricular Fibrillation (VF)

   • Mechanism: The most immediate cause of SCD, characterized by rapid, erratic electrical impulses that cause the ventricles to quiver instead of pumping blood.

2. Coronary Heart Disease (CHD)

   • Impact: The leading cause of SCD in adults, particularly those over 40. CHD can reduce blood flow, leading to ischemia and fatal arrhythmias.

3. Ischemic Heart Disease

   • Complications Post-MI: Including rupture of the myocardial free wall, septum, or a papillary muscle, which can lead to catastrophic heart failure or fatal arrhythmias.

4. Physical Stress or Severe Physical Activity

   • Risk: Can precipitate SCD in individuals with underlying heart conditions by increasing cardiac workload and potentially triggering a lethal arrhythmia.

5. Left Ventricular Dysfunction and Hypertrophy

   • Details: Impaired cardiac function and enlarged heart muscle both increase the risk for life-threatening arrhythmias.

6. Hypertension

   • Connection: Chronic high blood pressure can lead to left ventricular hypertrophy, a significant risk factor for SCD.

7. Fluid Imbalances

   • Hypovolemia and Hypervolemia: Both conditions can strain the heart and destabilize its rhythm, particularly if sudden or severe.

8. Hypertrophic Cardiomyopathy (HCM)

   • Overview: A common genetic heart disorder that often goes undetected and can cause thickening of the heart muscle, leading to arrhythmia.

9. Wolff-Parkinson-White Syndrome (WPW)

   • Description: A condition where an extra electrical pathway between the heart's upper and lower chambers causes rapid heartbeats.

10. Long QT Syndrome

    • Effect: A heart rhythm disorder that can cause fast, chaotic heartbeats, increasing the risk of VF and SCD.

11. Valvular Diseases

    • Specific Conditions: Aortic stenosis and mitral valve prolapse can alter blood flow dynamics and stress the heart, potentially triggering dangerous arrhythmias.

12. Substance Abuse

    • Cocaine: Known to provoke severe arrhythmic events and myocardial infarction, which can lead to SCD.

13. Congenital Disorders

    • Variety: Includes congenital anomalies of the coronary arteries or structural heart defects that predispose to arrhythmias.

Clinical Features of Sudden Death

Sudden death, particularly due to cardiac causes, often occurs with little to no warning but may be preceded by certain symptoms:

• Chest Pain: This is a classic sign of cardiac ischemia and can be a precursor to a myocardial infarction or acute coronary syndrome, both of which can lead to sudden death.

• Palpitations: Often indicative of an underlying tachyarrhythmia, which can rapidly deteriorate into more dangerous arrhythmias like ventricular tachycardia or fibrillation.

• Dyspnea: Associated with congestive heart failure, indicating worsening heart function which may predispose to fatal arrhythmic events.

• Fatigue and Syncope: General signs of cardiovascular compromise and can precede sudden arrhythmic deaths.

Treatment of Sudden Cardiac Death

Immediate and preventative treatments include:

• Implantable Cardioverter Defibrillator (ICD): For patients at high risk of fatal arrhythmias, an ICD can automatically detect and correct abnormal heart rhythms.

• Cardiopulmonary Resuscitation (CPR): Essential immediate response to sudden cardiac arrest, which can improve survival chances significantly if performed promptly.

• Survival Rate: Notably low outside hospital settings, underscoring the importance of public awareness and training in CPR and the availability of automated external defibrillators (AEDs).

Sudden Infant Death Syndrome (SIDS)

SIDS remains a complex and tragic phenomenon with unclear etiology, affecting infants primarily within the first year of life:

• Risk Factors: Include male gender, prematurity, young maternal age, and low socioeconomic status. Environmental factors like prone sleeping position, exposure to nicotine (both prenatally and postnatally), overheating, and unsafe sleeping environments are significant.

• Preventive Measures:

  • Sleep Position: Infants should be placed to sleep on their backs, which has been strongly associated with a decreased risk of SIDS.

  • Safe Sleeping Environment: A firm mattress, no loose bedding or soft toys that could lead to suffocation, and use of a sleep sack instead of blankets.

  • Avoid Overheating and Exposure to Smoke: Keeping the room at a comfortable temperature and ensuring a smoke-free environment.

  • Regular Prenatal Checkups: Encouraging healthcare engagement during pregnancy.

  • Breastfeeding: Recommended until at least the 6th month if possible, as it may provide protective factors.

  • Tummy Time: While awake and supervised, helps strengthen neck muscles, which can aid an infant in moving their head should they end up face down.