Embryology of the heart and fetal circulation

This is an old but awesome video on embryology of the heart and fetal circulation.

Complications of myocardial infarction

Myocardial infarction (MI) due to coronary artery disease is a leading cause of death in the United States.

Complications of MI include:
-Arrhythmic
-Mechanical
-Inflammatory

-Thrombo-embolic
-Circulatory/Shock



Arrhythmic Complications of MI:


About 90% of patients with MI develop some form of cardiac arrhythmia. These arrhythmias can be broadly classified into the following categories:

Supraventricular tachyarrhythmias
Accelerated junctional rhythms
Bradyarrhythmias
Atrioventricular (AV) blocks
Intraventricular block
Ventricular arrhythmias
Reperfusion arrhythmias

Mechanical Complications:

-Ventricular free wall rupture and pericardial tamponade
-Ventricular septal rupture
-Papillary muscle rupture with severe mitral regurgitation
-Left Ventricular Aneurysm

Inflammatory complications:

-Pericarditis: Occurs in 10% patients within the first 4 days of MI)
-Post-MI syndrome (Dressler syndrome): Occurs in 1-5% after MI and can present 2-3 weeks after MI.


Thrombo-embolic complications:

Occur secondary to regional myocardial hypokinesia and stasis as well as secondary to arrhythmias such as atrial fibrillation.

Circulatory/Shock:


Can be seen in right ventricular infarction (treatment is IVF) and in massive left ventricular infarction (treatment is supportive with careful administration of IVF.

Caisson Disease or Decompression Sickness

Caisson disease is also known as decompression sickness or diver's disease. When the body is subjected to high surrounding pressure (e.g. scuba diving), more than usual amount of Nitrogen gets dissolved in the blood. If the pressure is relieved suddenly, the dissolved Nitrogen can become gaseous quicker than the body can get rid of. These bubbles can lead to ischemia by blocking blood vessels. Clinical situations when such sudden depressurization can occur include scuba diving, caisson working, mining, flying in unpressurised aircraft, and extra-vehicular activity from spacecraft.

Depending upon the location of ischemia a variety of symptoms can results. Classically the symptoms are described as the bends, the chokes and the staggers!

The bends: refers to pain in the joints from ischemia of joint capsules
The chokes: refers to dyspnea
The staggers: refers to neurological symptoms.

Prevention:


-Divers should limit their ascent rate to about 10 metres per minute.
-Oxygen pre-breathing

Treatment:

-Administer 100% oxygen by face mask until re-compression with 100% oxygen until hyperbaric oxygen therapy is available.
-Treat dehydration

Kawasaki Disease

Diagnostic Criteria for Kawasaki Disease

Presence of fever for at least 5 days and at least four of five criteria:


- Bilateral conjunctival injection without exudate
- Polymorphous rash
- Changes in lips and mouth (Reddened, dry, or cracked lips, Strawberry tongue, Diffuse redness of oral cavity or pharynx)
- Changes in extremities (Reddening of palms or soles, Indurative edema of hands or feet, Desquamation of skin of hands, feet, and groin (in convalescence)
- Cervical lymphadenopathy (More than 15 mm in diameter, usually unilateral, single, non-purulent, and painful)

Exclusion of other conditions with similar clinical picture like:

• 
  
  Staphylococcal scalded skin syndrome, toxic shock syndrome
• 
  
  Scarlet fever
• 
  
  Stevens-Johnson syndrome
• 
  
  Drug reaction
• 
  
  Juvenile rheumatoid arthritis

NYHA Classification for Congestive Cardiac Failure

The New York Heart Association (NYHA) Functional Classification is used to grade the severity of congestive cardiac failure. Symptoms it refers to include dyspnea and chest pain.

NYHA Class	Symptoms
I	No symptoms and no limitation in ordinary physical activity, e.g. shortness of breath when walking, climbing stairs etc.
II	Mild symptoms (mild shortness of breath and/or angina) and slight limitation during ordinary activity.
III	Marked limitation in activity due to symptoms, even during less-than-ordinary activity, e.g. walking short distances (3-15 feet). Comfortable only at rest.
IV	Severe limitations. Experiences symptoms even while at rest. Mostly bedbound patients.

Complications of obesity

CVS - Hypertension, coronary artery disease, cor pulmonale, pulmonary hypertension of obesity, obesity related cardiomyopathy, atherosclerosis

CNS - Stroke, Benign intracranial hypertension

Neoplastic - Increased endometrial, prostate, gall bladder, breast and colon cancer

Endocrine - Non Insulin Dependent Diabetes Mellitus(NIDDM), abnormal lipid profile

GIT - cholecystitis, cholelithiasis, nonalcoholic steatohepatitis (NASH), fatty liver, gastro esophageal reflux disease(GERD)

Pulmonary - Obstructive sleep apnea, Pickwickian syndrome(hypoventilation)

Psychosocial -Depression, stigma,

Orthopedic - Osteoarthritis, slipped capital femoral epiphyses, Blount and Legg-Calvé-Perthes disease, backache

Gynecologic - Anovulation and infertility, hyperandrogenism and polycystic ovarian disease

Obstetric - Pregnancy induced hypertension, large baby

Surgical - Deep venous thrombosis, pulmonary embolism

Aspirin for MI/angina

162-325 mg of chewable aspirin should be promptly administered to patients who do not have bleeding tendency. Administration should not be delayed as the peak effect of aspirin can be seen as early as half hour after administration and it is important to prevent thrombus formation and propagation.

If the patient undergoes stenting 162-325 mg aspirin should be continued for 1 month after bare metal stent implantation, 3 months after sirolimus-eluting stent implantation, or 6 months after paclitaxel-eluting stent implantation.

Most subjects will get low dose (75-162 mg) all their life.

Novel Risk Factors for Atherosclerosis (CRP, Lipoprotein-a, Fibrinogen and Homocysteine)

CRP- C-reactive protein: High CRP reflects inflammation, and has been shown to correlate with the occurrence of myocardial infarction and peripheral arterial disease. 

Homocysteine levels: It is a well known fact that homozygous hyperhomocystinemia is associated with early atherosclerosis and stroke. However, approximately 5-7% of the general population have mild elevations of plasma homocysteine, and recent research have focussed on refuting or establishing if this population is at a higher risk for cardiovascular events. A number of treatments have been postulated for those with high homocysteine levels including folic acid and pantothenic acid. 

Fibrinogen: In recent studies high levels of fibrinogen have been found to be strongly related to cardiovascular events in apparently healthy individuals.

Lipoprotein-A: Lipoprotein A is an LDL like substance in the blood that remains bound to apolipoprotein A. It may promote atherosclerosis by its ability to be oxidized. Some studies have shown that Vitamin B3 (Niacin) can decrease its levels but the clinical significance is still unclear.

Syncope (Causes and Pathophysiology)

Syncope is defined as loss of consciousness due to decreased cerebral perfusion. Causes of syncope can be classified as Neuroregulatory, Arrhythmias and Hemodynamic.

 

A. Neuroregulatory causes of syncope.

A.k.a.vasovagal syncope this is caused by a sudden decrease in blood pressure. Prolonged standing is a common cause especially is the subject is dehydrated.

 

The low BP is sensed by carotid baroreceptors, that increase cardiac rate and contractility. On the other hand pressure receptors in the walls of the underfilled left ventricle may sense high-pressure and cause paradoxical bradycardia and lower contractility.

B. Arrhythmia as a cause of syncope.

Common arrhythmias causing syncope include supraventricular tachycardia (SVT), ventricular tachycardia (VT), ventricular fibrillation, and severe bradycardia (eg, heart block).

 

C. Hemodynamic syncope

 

The following Structure defects in the heart can cause syncope.

 

•Hypertrophic obstructive cardiomyopathy (HOCM) or aortic stenosis leading to left sided outflow obstruction

•Pulmonary hypertension may cause syncope when the right ventricle fails to pump against the high pulmonary pressure.
•Ischemic heart disease due to anomalous coronary artery origin, hypercholesterolemia, or acute inflammatory diseases such as Kawasaki disease and myocarditis.

•Pericardial tamponade can cause hypotension and syncope secondary to decreased pre-load (ventricles can not fill well).

Myocarditis classification

Myocarditis is inflammation of myocardium. It is usually viral and Cocksackie B is the commonest virus isolated. Myocarditis can be classified into the following 3 types based on pathologic findings per the Dallas Criteria (1987):

Active myocarditis - Characterized by abundant inflammatory cells and myocardial necrosis (subclassified into ongoing, resolving, or resolved myocarditis.)

Borderline myocarditis - Characterized by an inflammatory response that is too sparse for this type to be labeled as active myocarditis; degeneration of myocytes not demonstrated with light microscopy (subclassified into ongoing, resolving, or resolved myocarditis.)

Nonmyocarditis

William Morrow in Bundle Branch Block

You can distinguish between LBBB (Left Bundle Branch Block) and RBBB (Right Bundle Branch Block) simply by looking at the QRS morphology in V1 and V6.

If the QRS looks like W in V1 and M in V6 it is LBBB. (WiLLiaM)

If the QRS looks like M in V1 and W in V6 it is RBBB. (MoRRoW)

Extreme/severe hypertriglyceridemia

Severe hypertriglyceridemia will present as pain in abdomen due to pancreatitis.

Three classes of medications are appropriate for high triglyceride levels: fibric acid derivatives, niacin, and omega-3 fatty acids.  In addition high-doses of strong HMG CoA inhibitors (statins-simvastatin, atorvastatin, rosuvastatin) also lower triglycerides to some extent.

Relative Frequency of Major Congenital Heart Lesions

Relative Frequency of Major Congenital Heart Lesions

LESION	% OF ALL LESIONS
Ventricular septal defect	35–30
Atrial septal defect (secundum)	6–8
Patent ductus arteriosus	6–8
Coarctation of aorta	5–7
Tetralogy of Fallot	5–7
Pulmonary valve stenosis	5–7
Aortic valve stenosis	4–7
d-Transposition of great arteries	3–5
Hypoplastic left ventricle	1–3
Hypoplastic right ventricle	1–3
Truncus arteriosus	1–2
Total anomalous pulmonary venous return	1–2
Tricuspid atresia	1–2
Single ventricle	1–2
Double-outlet right ventricle	1–2
Others	5–10

Fixed Wide Splitting

Fixed Wide Splitting of the second heart sound is present in patients with Atrial Septal Defect.

Ductus dependent lesion

A newborn develops shock and cyanosis on day 2 of life. You must suspect a ductus dependant congenital heart disease and start Prostaglandin E1 infusion. Dont miss this: High yield for the USMLE.

Pheochromocytoma

Pheochromocytoma:

 

Pressure (BP)

Pain (Headache)

Perspiration

Palpitations

Pallor (example circum-oral due to vasoconstriction)

 

In the USMLE pheochromocytoma is a common answer to a number of questions. (In the exam the presenting feature will be palpitations and on examination there will be hypertension).

 

Chagas' Disease

Chagas' Disease : Caused by trypanosoma cruzi. Features include Cardiomegaly with Apical Atrophy.

A-Fib

Note the absence of the P wave. The other major change is that the heart rhythm is no longer regular. There is no pattern to the irregularity, so the rhythm of AF is called "irregularly irregular".

Pompe's disease

Pompe's Disease is a glycogen storage disease → cardiomegaly (α 1,4 Glucosidase deficiency: ↑ Glycogen)

Antiarrhythmics

Class IC antiarrhythmics

FEP
F - flecainide
E - encainide
P - propafenone

[no effect on Action Potential Duration]


Class III antiarrhythmics

BASI 
B - bretylium
A - amiodarone
S - sotalol
I - ibutilide


[K blockers-increase Action Potential Duration, ERP, QT]