Warfarin and Newer Oral Anticoagulants (NOACs) notes

Hey guys!
These are my notes from Harrison on Warfarin and Newer Oral Anticoagulants (NOACs).

Stop Antibiotic Abuse!

Hello Everyone,

It's been really long since the last post! Well it's been hectic all the way to and through residency.

I was recently researching on the topic of antibiotics while I stumbled upon this excellent piece of information cum approach by Dr.Strong on starting Anbiotics.

Well everyone should ask themselves these 12 questions before starting any antibiotic for one's patient and trust me you'll end up choosing the most appropriate one.
This is how we don't contribute to the Antibuse- "Antibiotic Abuse"( my personal neologism)

So now coming back to the questions, ask yourself these questions before you start any antibiotics,

1) What condition is being treated?
2) What are the commonly known bacterial species causing that condition?
3) Which antibiotic group is typically active against those?
4) What are the local resistance patterns for the chose antibiotic?
5)Will there be adequate organ penetration?
6) What is the preferred route of administration?
7)Any specific contraindication of the antibiotic to look out for?
8) Any required dose adjustment for coexisting renal or hepatic diseases?
9) Any specific drug interactions to be considered?
10) When on therapy anything that needs periodic monitoring?
11) How can the therapy be narrowed once bacterial sensitivities are available?
12) What will be the anticipated duration of the therapy?

Let's take a step towards stopping the rampant Antibuse.

That's all for now.

Let's learn Together!
-Medha Vyas.

Ring-enhancing lesion in an immunocompromised host

Hello everyone,

If it is a ring-enhancing lesion in an immunocompromised host, the most commonly seen etiologies are Cerebral toxoplasmosis (50%) and Primary central nervous system (CNS) lymphoma (30%).

But let's talk about the uncommon etiologies -

ECG quiz: ST elevation in aVR and ST depression in other leads

Quiz question: ST elevation in aVR and ST depression in other leads is suggestive of?

Trapezius and pericarditis.

Suppose a patient of 40 years of age male comes to you with complaints of  chest pain which is often heavy, squeezing and crushing.

You make up the diagnosis of MI based upon the symptoms in your mind. Proceeding for proper history of case you ask patient if the pain is radiating type.
Patient explains you that the pain is radiating and he is eventually experiencing pain in to the back of this some muscle. You find out that he is pointing towards the "Trapezius muscle" .

Now, this should raise an alarm in your mind. You should stop thinking about MI.

Reason?

Both NSTEMI and STEMI shows pain which is radiating in nature. Pain involves the central portion of the chest, sometimes epigastrium and occasionally it radiates to the arms. Less common involves back, neck, lower jaw. Pain can radiate as high as occipital area but never below umbilicus.
but it never radiates to trapezius.

Depicting exact lines of Harrison textbook of medicine.

"Radiation of discomfort to the trapezius is not seen in patients with STEMI and is  useful in correct diagnosis of pericarditis"

Now, why pain radiates to trapezius?

Pericarditis, as name suggests inflames the pericardial sac of the heart. This causes irritation of the vagus nerve supplying heart. Vagus nerve is affected because it is closely related to pericardial sac. Vagus nerve acts as the afferent nerve fibers. These fibers reaches nucleus tractus solitarius in the medulla oblongata. From there it comes downwards reaches cervical plexus C2, C3 and C4. From there, the nerve fibers formed supplies lower part of trapezius.

Trapezius nerve supply:
Upper part is supplied by the spinal accessory nerve.
Lower part is supplied by the nerves from C3 and C4 only.

Hence pain radiates to trapezius in pericarditis.

-Vipul and Ojas.

Update from IkaN: It's wrong to say that the pain of MI "never" radiates to the trapezius (which is in the back) because occasionally, pain of MI can radiate to the back. Also, pain radiating to the back should alarm you to a more serious diagnosis - aortic dissection. 

Can you find Asterixis in Non-Hepatic disorders?

Hello Awesomites! :D

This doubt came to my mind when I saw a case of COPD with asterixis.

 I used to think of asterixis with respect to hepatic disorders only.

 So let see is it so?

"Asterixis"is a non-specific sign. It is also known as flapping tremor.

It is a non-specific neurologic finding which may accompany organic delirium in a variety of metabolic or toxic disorders which interfere with cerebral metabolism.

It can be found in the cases with:-

1. Chronic pulmonary insufficiency

2. Uremia

3. Drug induced electrolyte imbalance

4. Arterial hypoxemia

5. Other reasons of electrolyte imbalance.

 Stay Awesome!

Upasana Y. :)

Authors' diary: Ponder

We were discussing a case today and learnt how important it is to take a second to think before we do something when dealing with patients.

Before you get a CT scan on the patient in the ER, stop and think - does the patient really need a CT scan? Will it get me the answers I'm looking for? Or will I need additional testing? Think of the harms of radiation exposure. Unless you don't want to rule out a hemorrhage that requires immediate intervention, do not order it STAT.

Dentinoenamel Junction

• DEJ appears as a scalloped line.
• The convexities of scallop are directed towards the dentine 
• The surface of dentine appears pitted
• DEJ provides strength to the union between enamel and dentin

Clinical Significance:

• Prevents shearing of enamel when functioning.
• Scalloping of the junction is seen more in the occlusal portion where masticatory stresses are high.

- Written by Anisha Valli

Enamel Lamellae

Thin, leaf-like structure that extends from enamel surface towards DEJ
Sometimes, they penetrate towards DEJ
They consist of organic material but with a little amount of mineral content.

Types of enamel lamellae:

• Type A: Lamelle composed of poorly calcified rod segments
• Type B: Lamelle consists of degenerated cells
• Type C: Lamelle arising in erupted teeth where cracks are filled with organic material, originating from saliva

Type A is restricted to enamel
Type B and C are restricted to dentine

Clinical Significance: 

• It is a site of weakness in a tooth.
• It forms a road of entry for bacteria to initiate caries.

Written By Anisha Valli

Hunter-Schrengar bands

The change in the direction of rods is responsible for Hunter Schregar bands.

These bands are the functional adaptation to occlusal masticatory forces.

Alternating, light and dark bands of varying width that can be seen in longitudinal cross-section under the obliquely reflected light.

Dark bands: Parazones
Light Bands: Diazones

The angle between the bands is 40 degrees

- Written by Anisha Valli

Zone Of Weil

Zone of Weil is present below the odontoblastic zone.

• Its a layer of 40um.
• It is also known as the sub-odontoblastic layer.
• It doesn't consist of cells.
• This zone is prominently seen in the coronal pulp.
• Cell-free zone decreases in size when dentin formation occurs at a rapid rate.
• The cell-free zone consists of a network of nerve fibres which lost their myelin sheath. This is known as Plexus of Rashkow.

Written by Anisha Valli

Mnemonics for special orthopedic tests

1) TEST: BRUDZINSKI 'S SIGN --

   *Description: Flexion of neck elicits reflexive flexion of knee.

   *Significance: suggests meningitis.

   * Mnemonic : a) Imagine as if the patient is in SKI position on the bed (neck and knee flexed) .
     b) The neck is stiff from the freezing in the snow.

2) DIX HALLPIKE MANEUVER --

   *Significance : suggests BPPV.

   *Mnemonic : Spike your drink and see the hall spin around you (vertigo) .

3) FINKELSTEINS 'S TEST :

  * Significance : for dequervain's tenosynovitis .

  *Mnemonic : a) Ask the patient to flick a coin of ten.
     b) The head's side of the coin has de (the) queen embossed on it.

4) HAWKIN'S TEST : 
   *Description : Internally rotate the shoulder to produce pain if rotator cuff pathology.
   *Mnemonic :Imagine a hawk flying in circles (rotate) , waiting to attack the shoulder of its prey.

5) LHERMITTE'S SIGN: 
   *Description : Passive forward flexion of head causes electric sensation down the spine.

   *Mnemonic : Imagine a hermit (sadhu)  giving his blessings (aashirwaad)  which induces some electric power down your body.

6) LACHMAN TEST:

   *Significance : indicates anterior cruciate ligament injury.

   *Mnemonic : Imagine anterior cruciate ligament to be a latch which keeps the tibia and femur locked to each other.

7) O'BRIEN TEST:
    *Description : With shoulder at 90 degrees flexion, instruct patient to point thumb at ground and resist downward force. Repeat with palm facing upwards.

  *Significance : Pain suggests labral tear.
   *Mnemonic : a) This is a story of O'Brien who worked as a labourer.
     b) He got thumbs down for his work.
     c) So he had to beg (with palms facing upwards) to make end's meet.

8) SPURLING TEST    

    *Significance : Tingling or pain along cervical nerve root suggests cervical radiculopathy.

    *Mnemonic :a) Spurling test is for spine.
     b)  Imagine if there are spurs formed in spine, they will compress the spinal cord causing radiculopathy.

9) McMURRAY'S TEST :

   *Significance : positive test suggests meniscal tear.

  * Mnemonic : a) Tennis players are very vulnerable to meniscal tear.
     b) Imagine Andy Murray to be suffering from meniscal tear.
     c) Also Mc Murray and meniscus both have M and C.

10) PHALEN 'S TEST :
 
   *Description : Instruct patient to bring dorsal aspect of hands together.  
    *Significance : Tingling or paresthesia in lateral 3.5 fingers suggests carpal tunnel syndrome.

    * Mnemonic : a) Imagine a felon who is handcuffed with dorsal aspect of his hands together.
   b)  The handcuffs are tight and compressing his median nerve causing tingling and numbness.

Submitted by Abuzar Asif

Mnemonics and basics of ECG interpretation

Hello !! 

Many people think ECG interpretation is hard i will take you through the basics of it.

To understand how to interpret the ECG you must first understand the basics which is out of the scope of this scope.

To interpret an ECG the following are the most important:

1. Understanding the basics 

2. Systematic approach for interpretation

SOME BASICS

ECG WAVEFORMS

- What do the waves represent ?

Adapted from: https://meds.queensu.ca/central/assets/modules/ts-ecg/waves_and_complexes.jpg

WAVES AND INTERVALS PICTORIAL REPRESENTATION

Adapted from: https://ecgwaves.com/topic/ecg-normal-p-wave-qrs-complex-st-segment-t-wave-j-point/

- What do the boxes represent ? 

Each small box in the ECG paper is 1 mm = 0.1 mV = 0.04 secs

Each large box in the ECG paper is  5mm = 0.5 mV = 0.20 secs (0.04 X 5)

Adapted from: ECG interpretation made incredibly easy —5th ed 

SYSTEMATIC INTERPRETATION

1. Heart rhythm

- Use paper and pencil/pen method for determination of the heart rythm

 

Adapted from: ECG interpretation made incredibly easy —5th ed 

- Determine whether it is a sinus rhythm ? (in which each QRS complex is preceded by a p wave)

- Determine whether the rhythm is regular or not:

- Types of rhythms:

a. Regularly regular rhythm: In a normal individual

b. Regularly irregular rhythm: Sinus arrhythmia

c. Irregular irregular rhythm: Atrial fibrillation

2. Heart Rate

- Atrial rate : between 2 P waves

- Ventricular rate : between 2 R waves

- Can be calculated depending on whether the rhythm is regular or irregular

- If the rhythm is regular the following methods can be used:

a.  300 method

In this take 300 divided by number of large boxes between 2 R waves

Example: If the number of boxes between 2 R waves is 3 then the Rate would be 300/3 = 100 beats/min.

b. 1500 method

In this take 1500 divided by the number of small boxes between 2 R waves

Example: If the number of boxes between 2 R waves is 14 then the Rate would be 1500/14 = 107 beats/min.

c. Rapid estimation method

Use this only if the rhythm is regular

Using the number of large boxes between R waves or P waves as a guide, you can rapidly estimate ventricular or atrial rates by memorizing the sequence “300, 150, 100, 75, 60, 50.”

For an Irregular rythm:
- Use the rythm strip / Lead II and count the number of R waves in 6 seconds (30 large boxes ) and multiply by 10.

3. Cardiac Axis

- Determined using lead I and II / aVF

- Determine the cardiac axis : the easiest way is to use the thumb rule

- Left thumb represents lead 1

- Right thumb represents lead 2 or lead aVF

- Mnemonics for the causes of axis deviation RAD RALPH the LAD from the VILLA

RAD - Right axis deviation causes

R- Right ventricular hypertrophy

A- Anterolateral MI

LPH- Left posterior hemiblock

LAD - Left axis deviation

V- Ventricular tachycardia

I- Inferior MI

L- Left ventricular hypertrophy

LA- Left Anterior fascicular block

4. Evaluate P wave

- P waves should be upright in leads I and II, inverted in aVR

- Are p waves present before every QRS complex? if yes; sinus rhythm

- P waves may be absent in; atrial fibrillation

- Normal P wave : <0.10 sec (2.5 small boxes)

- Common Abnormalities of P wave

Bifid/notched P waves (p mitrale) : Left atrial enlargement - classically due to mitral stenosis

Peaked P waves (p pulmonale) : Right atrial enlargement - due to Pulmonary Hypertension

5. Duration of PR interval

- The PR interval is the time from the onset of the P wave to the start of the QRS complex 

- It reflects conduction through the AV node

- Normal duration : 3-5 small boxes (0.12 to 0.20 secs)

- Determine if the duration is normal

- Common abnormalities of PR interval

a. Can be prolonged in: AV block

b. Can be short in: Pre-excitation syndromes e.g in Wolff-Parkinson-White syndrome; which involve the presence of an accessory pathway connecting the atria and ventricles.The accessory pathway conducts impulses faster than normal, producing a short PR interval.

6. Duration of the QRS complex

- Normal duration : 2-3 small boxes (0.08-0.12 secs)

- Determine if the duration is normal

- Are all QRS complexes of same size and shape ?

- Does a QRS complex appear after every p wave ? if not consider an AV block (second degree AV block); in which the PR-interval progressively gets longer until a QRS is dropped and only the p-wave is present

- Common abnormalities of QRS complex

a. QRS deflections; Exaggerated QRS deflections indicate ventricular hypertrophy 

- The voltage criteria for left ventricular hypertrophy are fulflled when the sum of the S and R wave deflections in leads V1 and V6 exceeds 35 mm (3.5 mV) ( 7 large boxes )

- Right ventricular hypertrophy causes tall R waves in the right ventricular leads (V1 and V2)

- Diminished QRS deflections occur when pericardial effusion or obesity electrically insulates the heart

b. Narrow QRS complex morphology (<0.08 secs)

- Atrial flutter

- Junctional tachycardia

- Note : normal sinus rhythm also has a narrow QRS complex morphology

c. Broad/wide complex QRS complex morphology (>0.12 secs)

- Bundle branch block (BBBB) : LBBB or RBBB

- Hypokalemia

- Poisoning with sodium-channel blocking agents (e.g. tricyclic antidepressants) - remember this also gives you a dominant R wave in lead avR.

7. ST segment

- The ST segment is the flat, isoelectric section of the ECG between the end of the S wave and the beginning of the T wave.

- It represents the interval between ventricular depolarization and re polarization.

- The most important cause of ST segment abnormality (elevation or depression) is myocardial ischemia or infarction.

The causes of ST elevation can be remembered using the mnemonic ELEVATION

Electrolyte abnormalities

Left bundle branch block

Aneurysm of left ventricle

Ventricular hypertrophy

Arrhythmia disease (Brugada syndrome, ventricular tachycardia)

Takotsubo/Treatment (iatrogenic pericarditis)

Injury (myocardial infarction/ischaemia or cardiac contusion)

Osborne waves (hypothermia or hypocalcemia)

Non-atherosclerotic (vasospasm or Prinzmetal’s angina)

The causes of ST depression can be remembered using the mnemonic DEPRESSED ST

Drooping valve (MVP)

Enlargement of LV with strain

Potassium loss (hypokalemia)

Reciprocal ST- depression (in I/W AMI)

Embolism in lungs (pulmonary embolism)

Subendocardial ischemia

Subendocardial infarct

Encephalon haemorrhage (intracranial haemorrhage)

Dilated cardiomyopathy

Shock

Toxicity of digoxin, quinidine

8. Evaluate T wave

It represents ventricular repolarisation

NB: 

Upright in all leads except aVR and V1

Amplitude <5mm (5 small boxes) in limb leads, <15mm (3 large boxes) in precordial leads

- Are T waves present ?

- Do they have normal shape ?

- Do they have normal amplitude?

- Do they have same deflection as QRS complexes ?

- Common T wave abnormalities

a. Inverted T wave

- Can be remembered by the mnemonic INVERT

Ischemia, raised ICP

Normality [esp. young, black]

Ventricular hypertrophy

Ectopic foci [e.g. calcified plaques], classic pulmonary Embolism 

RBBB, LBBB

Treatments [digoxin]

b. Tall/peaked T waves

- Classically seen in Hyperkalemia

c. Hyperacute T waves

- Seen in early stages of ST elevation MI (STEMI)

d. Biphasic T waves

-Ischaemic T waves go up then down

-Hypokalaemic T waves go down then up

e. Flat T wave

- Ischaemia

- Hypokalemia

9. Determine the duration of the QT interval

QT interval : is the time from the start of the Q wave to the end of the T wave. It represents the time taken for ventricular depolarisation and repolarisation, effectively the period of ventricular systole from ventricular isovolumetric contraction to isovolumetric relaxation

- QT interval is inversely proportional to heart rate i.e as the HR increases the QTi decreases and vice versa

- The QT interval should be measured in either lead II or V5-6

- Determine if the QT interval is normal ? (normal = 0.36 to 0.44 secs = 9-11 small boxes)

- Corrected QT interval (QTc)

-- Due to the variations of the heart rate : The corrected QT interval estimates the QT interval at a heart rate of 60 bpm.
-- The following formula can be used to calculate the QTC = QT interval / √ RR interval (Bazzet's formula) 
-- RR interval = 60/Heart rate
-- Note: there are many formulas which can be used for calculation of but this is probably the easiest one.
-- QTc is prolonged if > 0.44 secs in men or > 0.46 secs in women

-- QTc > 500 is associated with increased risk of torsades de pointes

- Causes of prolonged QTc > 0.44 secs

Hypokalaemia

Hypomagnesaemia

Hypocalcaemia

Hypothermia

Myocardial ischemia

Post-cardiac arrest

Raised intracranial pressure

Congenital long QT syndrome

Drugs - quinidine, amiodarone, TCA's

- Causes of a short QTc < 0.36 secs

Hyperkalemia

Hypercalcaemia

Congenital short QT syndrome

Digoxin effect

The End !!

Please note that this is not everything that you need to know , and this article doesn't cover everything about the ECG, it just covers the basics and the most common abnormalities that can be found on an ECG.

But for sure ! It has just enough information which can help anyone understand and interpret and ECG.

Mohammad Farouq,

Final year medical student, MUHAS.