Question 4

A 66-year-old male presents to hospital with hypotension, having had intermittent chest pain throughout the day. He develops runs of broad complex bradycardia requiring adrenaline boluses to maintain output. He is alert, and not in respiratory distress. His blood pressure is 90/40 mmHg, and his heart rate is 113 beats/min.

Past medical history includes Type 2 diabetes mellitus (T2DM) with end stage kidney disease. Baseline blood tests include K+ 5.8 mmol/L, urea 20 mmol/L, creatinine 430 μmol/L, Hb 96 g/L. Further questioning reveals a 4-day history of loose, dark bowel motions.

Blood gas results are shown below:

Parameter Admission value     Adult Normal Range
FiO2 0.28  
pH 7.14* 7.35 – 7.45
pO2 78 mmHg  
pCO2 31.0 mmHg* 35.0 – 45.0
SpO2 94%  
Bicarbonate      10.3 mmol/L* 22.0 – 26.0
Base Excess -14 mmol/L* -2.0 – +2.0
Lactate 3.1 mmol/L* 0.5 – 1.6
Parameter Patient Value        Adult Normal Range
Sodium 133 mmol/L* 135 – 145
Potassium 6.9 mmol/L* 3.5 – 5.0
Chloride 109 mmol/L* 95 – 105
Glucose 16.8 mmol/L* 3.5 – 6.0
Urea 41.5 mmol/L* 3.0 – 8.0
Creatinine 489 μmol/L* 45 – 90
Magnesium 0.95 mmol/L 0.75 – 0.95
Albumin 35 g/L 35 – 50
Calcium corrected       2.40 mmol/L 2.12 – 2.62
Phosphate 1.5 mmol/L 0.8 – 1.5
Creatinine Kinase 1692 U/L* 55 – 170
Hs troponin 6501 ng/L* 0 – 34
Cortisol 438 nmol/L 170 – 500
CRP < 3 < 5
     
Parameter Patient Value Adult Normal Range
Haemoglobin 66 g/L* 120 – 160
Mean Cell Volume 93 fL 80 – 99
White Cell Count 14.2 x 109/L* 4.0 – 11.0
Platelet count 258 x 109/L 150 – 350
     
Parameter Patient Value Adult Normal Range
Prothrombin time 14.5 sec 12.0 – 16.5
INR 1.1 0.9 – 1.3
APTT 32.0 sec 27.0 – 38.5
Fibrinogen 4.1 g/L* 2.0 – 4.0

a)    List the abnormalities and explain the potential cause of each.    (60% marks)

The patient’s ECG (ECG 4.1) is shown on page 5. (Image removed from paper.)  

ECG from Circulation


b)    List the abnormal ECG findings and list the likely diagnosis.    (20% marks)

c)    List how you would confirm this diagnosis.    (20% marks)
 

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College answer

Not available.

Discussion

Without official college answers to refer to, the (broad) differentials presented by this SAQ were entirely to the imagination of the author, with predictably disastrous consequences.

First, let us list the abnormalities. The question does not specify where to get them from (just the bloods?), or how many to list; but this is for 60% of the marks, so the response needs to be comprehensive.

Thus, from the stem:

  • Hypotension and tachycardia is due to cardiogenic shock/heart failure
  • The chest pain is almost certainly ischaemic in origin
  • The broad complex bradycardya is likely referring to complete heart block, which could have broad complexes (originating below the AV node)
  • The recent bloods given to us demonstrate hyperkalemia and biochemical findings supporting the history of chronic kidney disease, including the anaemic haemoglobin.
  • The history of what sounds like melaena suggests there has been upper GI bleeding

From the gas:

  • The ABG demonstrates hypoxia and an incompletely compensated metabolic acidosis (i.e. a respiratory and a metabolic acidosis). To be systematic about things, 
    • The A-a gradient is raised (713×0.28)- (31×1.25) = 160
    • (0.35 x 713) - (52 x 1.25) - 82 = 102.55 mmHg
    • There is acidaemia
    • There is a severe metabolic acidosis (SBE -14)
    • The CO2 is incompletely compensatory; the expected CO2 is (10.3×1.5)+8 = 23.45, or 26 by the Copenhagen method (40-14=26). Either way this means there is also a respiratory acidosis.
  • The hypoxia can be accounted for by pulmonary oedema
  • The metabolic acidosis can be explained by the shock state
  • There is a raised lactate, which likely represents either poor tissue perfusion or lactic acidosis due to all those adrenaline boluses

From the rest of the bloods:

  • There are urea and creatinine changes consistent with a slightly worse renal function, which was already very bad. Specifically, the raised urea (doubled from the last bloods) supports the idea that the patient is bleeding from the upper GI tract.
  • The hyperkalemia is likely related to the renal failure, and is probably contributing to the rhythm disturbance
  • The troponin and CK are raised probably because the patent has had some coronary ischaemia, though it is difficult to interpret in the context of the renal function being so poor.
  • The anion gap is relatively normal (133-109-10.3 = 13.7), which suggests that renal failure is responsible for most of the metabolic acidosis.
  • The haemoglobin is low, consistent with an upper GI bleed
  • The WCC is trivially elevated, a finding so nonspecific as to be essentially uninterpretable.

The rest of the bloods are essentially normal.

"List the abnormal ECG findings" and "list the likely diagnosis" is a much harder task, even if one assumes the second half of the question asked to give the likely diagnosis instead (it is of course possible that "list the likely diagnosis" actually meant "give a list of differentials").

 The college had removed the ECG from their paper, so this ECG comes from Falk (2005). Its main feature is a low-voltage QRS, with poor R wave progression. Addiitonal possible findings which might have appeared in the college EC could have been AV conduction abnormalities (eg. a first degree heart block) or a "pseudoinfarct" pattern (Cheng et al, 2013). Why was this ECG chosen to replace the one in the paper? Because the fascinating forensic task of reconstituting this SAQ has led the author to look for some kind of a grand unifying diagnosis which is associated with renal failure, one which produces ECG-detectable cardiac abnormalities, and which could be related to the upper GI blood loss. This winding path had led to amyloidosis. This is supported by uneducated Google searches:

  • Amyloidosis is associated with chronic kidney disease
  • Cardiac amyloid is known to often cause conduction abnormalities (Roy, 2018)
  • Amyloidosis has gastrointestinal manifestations which can present as gastric bleeding (Chan et al, 2021)

This, of course, could be completely wrong. But the reader should note that listing ECG abnormalities and interpreting the data was worth most of the marks, and the diagnosis was one tiny fraction (perhaps 10% of the total). It is of course possible that "list the likely diagnosis" actually meant "give a list of differentials"

The investigations to confirm or exclude this disease would be:

  • TTE:  In combination with echo findings of LV thickening, this ECG would be strongly suggestive of an infiltrative cardiomyopathy.
  • Cardiac MRI
  • Endocardial biopsy 

References

Falk, Rodney H. "Diagnosis and management of the cardiac amyloidoses." Circulation 112.13 (2005): 2047-2060.

John, Roy M. "Arrhythmias in cardiac amyloidosis." The Journal of Innovations in Cardiac Rhythm Management 9.3 (2018): 3051.

Cheng, Zhongwei, et al. "The findings of electrocardiography in patients with cardiac amyloidosis." Annals of Noninvasive Electrocardiology 18.2 (2013): 157-162.

Chan, Rachael, and Stephanie Carpentier. "Gastric amyloidosis presenting as acute upper gastrointestinal bleeding: a case report." BMC gastroenterology 21.1 (2021): 1-4.