History of Hypertrophic Cardiomyopathy (HOCM), with Tachycardia and High Lactate

A patient under 40 with h/o HOCM and implantable cardioverter-defibrillator (for secondary prevention of VF arrest that occurred during exertion) presented with chest pain, diaphoresis, and tachycardia.  Earlier in the day, the patient had been physically active, which resulted in dizziness, SOB and diaphoresis.  Then later, there was alcohol consumption associated with further physical exertion.  The patient presented clutching the chest, dizzy, SOB, diaphoretic.  BP was 165/109 (a good example of shock in which the BP is maintained by high systemic vascular resistance).

Here is her ED ECG:

There is a narrow complex (QRS duration =113 ms) tachycardia at a rate of about 160.  There are no definite P-waves.  It appears to be paroxysmal SVT.  There is very high voltage and secondary repolarization (ST-T) abnormalities.

The Bedside Cardiac Ultrasound is shown here:


This shows the very hypertrophic walls, and the consequent very small left ventricular chamber collapsing on itself.  There is very little opporunity for the heart to fill with blood, and probable obstruction of aortic outflow as well.

The patient was given adenosine 6 mg, 12 mg, 12 mg, and 18 mg without any lasting effect.

Lactate returned at 8.3 mEq/L, consistent with shock.

Then an esmolol double bolus (each bolus = 500 mcg/kg) and drip was given, with immediate slowing of heart rate.  The patient was given a normal saline fluid bolus.

The heart rate immediately slowed and here is the ECG at t = 45 min:

Sinus tach with heart rate about 100.  High Voltage and secondary ST-T abnormalities.

The patient stabilized with a BP of 107/58 and pulse of 100 and felt much better.

Later that day:

Sinus rhythm.  LVH with typical repolarization abnormalities.  Though this ECG is diagnostic of LVH, it is not specifically diagnostic of HOCM.  The signatures of HOCM, besides LVH, are tall R-waves in septal leads (septal hypertrophy) and deep S-waves in lateral leads (reciprocal to septal hypertrophy, such as in the ECG from another patient below. 

Here is an example of HOCM with septal R-waves in the right precordium (different patient):

There is massive voltage with corresponding repolarization abnormalities.  There is very high voltage R-waves in right precordial leads, highly suggestive of septal hypertrophy.  The ST segments are depressed, discordant to the large R-wave.  This is unlike most LVH, in which the right precordial S-waves are deep, with discordant ST elevation.)  This is highly suspicious for hypertrophic cardiomyopathy with asymmetric septal hypertrophy (HOCM).   To see this entire case, with ultrasounds, go to this post.

Back to this case:

Interrogation of the IVCD revealed that the heart rate gradually slowed after esmolol (there was no sudden conversion of rhythm to suggest re-entry).  Thus, the initial ECG is believed to have had a rhythm of sinus tachycardia.

Whether sinus tach or SVT, beta blockade is an ideal therapy in this situation, along with fluids.  The LV's pump function is too vigorous, causing collapse.  And the fast heart rate leaves no time for cardiac filling.  The left atrial pressure is too low to allow good preload of the LV.  Therefore, one should increase preload by increasing left atrial pressure (by giving fluids), and both 1) slow the heart rate to allow for better filling and 2) decrease pump function to prevent obstruction of outflow and also allow for better filling (by giving beta blockade, in this case esmolol, as short-acting beta-1 blocker that can be discontinued if there are adverse events).

The high lactate shows how this patient is very volume dependent.  Dehydration can set off a spiral of low stroke volume, then further catecholamine output with consequent increased myocardial contractility, and thus LV chamber collapse, with subsequent obstruction of outflow and worse filling.  The vicious cycle needs to be broken.

Outcome:

The patient did very well and was instructed to not let herself get dehydrated.  It is uncertain if she was discharged on a beta blocker, but this is one potential therapy to help prevent recurrence.