Wednesday, March 1, 2023

ECG Blog #366 — Diltiazem didn't work ...

The ECG and long lead II rhythm strip in Figure-1 — was obtained from a COVID positive patient with persistent tachycardia not responding to Diltiazem.
  • How would YOU interpret this tracing?
  • How to manage the patient?

Figure-1: The initial ECG — obtained from a patient with persistent tachycardia. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:
As always — I favor beginning my interpretation with assessment of the long lead rhythm strip at the bottom of the tracing. By the Ps, Qs, 3R Approach (See ECG Blog #185):
  • Regarding Regularity — the rhythm is irregularly irregular.
  • The Rate of the rhythm is rapid — with the R-R interval between 1.5 and 2.5 large boxes for most complexes on the tracing. This corresponds to an average heart rate of ~120/minute!
  • The QRS is narrow in all leads — so the rhythm is supraventricular.

  • P waves are present throughout the tracing. P wave morphology changes — almost from 1 beat to the next (See colored arrows in the long lead II rhythm strip of Figure-2). That said — P waves do appear to be Related to neighboring QRS complexes, as each of the 21 beats on the tracing is preceded by a P wave with reasonable PR interval.

Figure-2: I've color-coded P waves from Figure-1 according to P wave morphology (See text).

Putting It All Together:
The finding of a fast, irregularly irregular supraventricular rhythm — in which P waves precede neighboring QRS complexes, but with a constantly changing P wave morphology — defines the rhythm as MAT ( = Multifocal Atrial Tachycardia).
  • NOTE: For clarity — I've color-coded P waves in the long lead II rhythm strip according to morphology. The fact that there are no less than 11 changes in P wave morphology (ie, 11 different colors out of a total of 21 beats) — confirms the constantly changing P wave morphology characteristic of MAT.

PEARLS about MAT: 
Consider the following features regarding MAT:
  • MAT is not a common diagnosis. As a result, in order to differentiate MAT from the much more commonly encountered irregularly irregular rhythm (which is AFib) — we need to be certain we are seeing multiple different P wave morphologies that are constantly changing. The 11 different colors for the arrows in Figure-2 make it evident that we are! 
  • NOTE: In addition to the constantly changing P wave shapes — the PR interval in the long lead II is also constantly changing! This is another way to confirm that we are indeed seeing P waves arising from different atrial sites that change from one-beat-to-the-next.

  • MAT almost always occurs in one of 2 common predisposing settings. These 2 settings are: i) In patients with severe, often longstanding pulmonary disease; and/or, ii) In acutely ill patients with multi-system disease (ie, sepsis, shock, electrolyte and/or acid-base disorders). As a result — I’m reluctant to diagnose MAT in the absence of one of these 2 settings.

  • To EMPHASIZE: It is EASY to overlook the diagnosis of MAT because: i) The diagnosis is not common (It is less common than many clinicians appreciate)andii) P waves with changing morphology may not always be evident in all 12 leads. As a result — IF the 1 lead you are monitoring happens to be one in which P waves are not well seen — then you might assume the irregular rhythm in front of you was AFib. Remember — 12 leads are better than one! It is especially important to always obtain a 12-lead ECG whenever you see an irregularly irregular rhythm in association with one of the above 2 predisposing conditions that MAT is prone to occur in. 
  • MAT is not a Wandering Pacemaker. MAT is a pathologic rhythm in which P wave morphology changes from one-beat-to-the-next. In contrast — a wandering pacemaker is often a benign rhythm (if not a normal variant) — in which the heart rate is slower and there is a gradual shift in P wave morphology over a period of several beats, most often occurring in an otherwise healthy and asymptomatic patient.

  • Clinically, the importance of recognizing MAT — is that treatment is different than the treatment of AFib. Most of the time, the heart rate with MAT will not be excessive — so all that is usually needed, is to "find and fix" the underlying predisposing cause (ie, optimize oxygenation; treat sepsis, electrolyte or acid-base disorders). This is distinctly different than treatment objectives for AFib, which in addition to correcting the cause (and addressing anticoagulation issues) — consist of rate slowing, and medical or electrical cardioversion interventions. NOTE: Today's case is an exception to the above generality — in that the MAT rhythm in Figure-2 is surprisingly fast (ie, ~120/minute) — so that this is one of the occasional times when MAT does merit consideration of rate-slowing medication.

Applying the Above to Today's Case:
In addition to being Covid-positive — the patient in today's case had longstanding COPD. He was wheezing, and required supplemental oxygen.
  • The diagnosis of MAT is clearly supported in today's case by the clinical setting: i) The patient was symptomatic from longstanding pulmonary disease; ii) He was acutely ill, with a rapid irregular SVT not responding to medication; and, iii) He was Covid-positive — potentially with significant pulmonary involvement from this.

  • IV Verapamil or Diltiazem are good initial choices for MAT — when rate-slowing medication is needed (Today's patient was not responding to Diltiazem). It's important to optimize K+ and Mg++ levels (IV magnesium is at times a helpful adjunct). If the patient is not frankly wheezing — judicious use of an IV ß-blocker may help to control the ventricular rate.
  • Realistically — optimal rate control of this patient's MAT may not be possible until improvement of his pulmonary disease and underlying conditions.


Acknowledgment: My appreciation to Stanislav Galkin (from Enniskillen, Northern Ireland) for the case and this tracing. 


ADDENDUM (3/1/2023) — Additional material relevant to today's case:
  • How Covid-positivity in today's case may affect the heart.
  • Additional material on MAT.

Cardiac Manifestations of Covid-19:
Manifestations of heart disease may be seen in patients with Covid-19, including signs of myocardial injury. That said — many patients with Covid have surprisingly few symptoms of cardiac involvement — with detection of myocardial injury becoming evident primarily by cardiac testing (ie, from troponin elevation, cardiac arrhythmias, Echo abnormalities — or other forms of cardiac imaging). Myocardial injury with Covid may arise from a number of potential causes — which include:
  • Acute myocarditis.
  • Takotsubo (ie, Stress) Cardiomyopathy.
  • Acute MI.
  • Acute Right Heart Strain.
  • Hypoxic injury (from pneumonia or other acute pulmonary complication).
  • Acute pulmonary embolus.
  • ARDS (Adult Respiratory Distress Syndrome).
  • SIRS (Systemic Inflammatory Response Syndrome).
  • Microvascular dysfunction — cardiac vasculitis — intravascular thrombosis.

Although acute Myocarditis is often suspected as the cause of troponin elevation in Covid-positive patients — documented viral myocarditis caused by Covid appears to be much less common than initially thought (Up-to-Date — Caforio et al — Jan, 2023)
  • In Covid patients with myocardial injury (be this from myocarditis or otherwise) — disease severity and prognosis tend to be proportional to the amount of troponin elevation — with better prognosis in those patients with fewer symptoms and limited (if not minimal) troponin elevation. That said — assessment of the direct effect that Covid has on outcome is difficult to determine, especially in older hospitalized patients more likely to have known (or previously undetected) underlying forms of cardiac or pulmonary disease.


Additional Points on MAT:

ECG recognition of MAT (3:20 minutes Video).


Figure-3: Summary of KEY points related to MAT.


Related ECG Blog Posts to Today’s Case:

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
  • ECG Blog #185 — Review of the Ps, Qs, 3R Approach for systematic rhythm interpretation.

  • ECG Blog #199 — for Review of MAT.
  • ECG Blog #65 — for an example of MAT in a patient with chronic pulmonary disease (plus more on the differential diagnosis of MAT).
  • ECG Blog #200 — for an example of Wandering Atrial Pacemaker.

I link to 2 additional illustrative Cases taken from Dr. Smith’s ECG Blog. For each of these posts — Please scroll down to the bottom of the page to see My Comment. These cases provide insight to assessment for MAT:
  • The January 5, 2020 post in Dr. Smith’s ECG Blog — for an example of MAT.
  • The September 30, 2019 post in Dr. Smith’s ECG Blog — for an example of “MAT”, but without the tachycardia ...

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