ECG: Multifocal Atrial Tachycardia

1. Physician’s Meet
M3 unit
Dr. S Sundar’s Unit
ECG of the week
Dr. Deepu Sebin

3. 12 lead ECG
Sinus Rhythm
Rate = 62/m
Axis = +30
Pace maker spikes +
PR Interval = 0.12
QRS duration = 0.16sec
LBBB pattern
Concordent ST evelevation in V4,V5,V6,1,aVL
ST segment depression in 111,aVF

4. AnteroLateral MI with LBBB

5. LBBB and MI
Left bundle branch block (LBBB) is present in
approximately 7 percent of acute infarctions
Patients with LBBB have more comorbid conditions, are
less likely to receive therapy, and have an increased risk
for in-hospital death compared with patients with no BBB.
- - - .
TI Bundle branch block and in hospital mortality in acute myocardial infarction National Registry of
2 .
Myocardial Infarction Investigators
- ; ; ; ;
AU Go AS Barron HV Rundle AC Ornato JP Avins AL
- 1998 1;129(9):690-7.
SO Ann Intern Med Nov

6. The sequence of repolarization is altered in LBBB, with
the ST segment and T wave vectors being directed
opposite to the QRS complex. These changes may mask
the ST segment depression and T wave inversion induced
by ischemia.
The diagnosis of an acute MI or ischemia can occasionally
be made in a patient with underlying LBBB if certain ST-
T changes are seen, particularly if the ST-T vectors are in
the same direction as the QRS complex.

7. Concordant v/s Discordant
changes

8. Sgarbossa Criteria
The three ECG criteria with an independent value in the
diagnosis of acute infarction and the score for each were:
ST segment elevation of 1 mm or more that was in the same
direction (concordant) as the QRS complex in any lead —
score 5.
ST segment depression of 1 mm or more in any lead from
V1 to V3 — score 3.
ST segment elevation of 5 mm or more that was discordant
with the QRS complex (ie, associated with a QS or rS
complex) — score 2

Electrocardiographic
- . -1
diagnosis of evolving acute myocardial infarction in the presence of left bundle branch block GUSTO
( )
Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries
.
Investigators
- ; ; ; ; ; ; ;
AU Sgarbossa EB Pinski SL Barbagelata A Underwood DA Gates KB Topol EJ Califf RM
Wagner GS
- 1996 22;334(8):481-7
SO N Engl J Med Feb

9. At a score-sum of 3, these criteria have a specificity of
90% for detecting a myocardial infarction.

10. A Sgarbossa score of ≥ 3 was highly specific (ie, few false
positives) but much less sensitive (36 percent) in the
validation sample in the original report. Similar findings were
noted in a subsequent meta-analysis of 10 studies of 1614
patients in which a Sgarbossa score of ≥ 3.

11. Additional Findings
The presence of
deepTwaveinversions
in leads with a
predominantly negative QRS complex (eg, V1-V3) is
highly suggestive of evolving ischemia or MI.
The presence of
QRcomplexes
in leads I, V5, or V6, or
in II, III, and aVF with LBBB strongly suggests
underlying infarction.
Pseudonormalization of previously inverted T waves is
suggestive but not diagnostic of ischemia.

12. Additional Findings
An anterolateral MI should be suspected if
newS
waves
appear in leftward leads (I, aVL, and V6) in a patient with
preexisting common LBBB.
Underlying MI is also suggested by notching of the
ascending part of a wide S waves in the mid-precordial
leads ( '
Cabrerassign
) is present.

13. Additional Findings
Cabrera's sign
refers to prominent (0.05 sec) notching in the ascending
limb of the 3 4 .
SwaveinleadsV andV
Chapman's sign :
a similar finding is prominent notching (>/= 0.05 sec ) of
the ascending limb of the 5 6 .
RwaveinleadV orV
These signs have a specificity that approaches 90 percent.
However, there may be a high degree of interobserver
variability in accurate identification and their sensitivity is
quite low.

14. Serial ECG changes — 67 percent sensitivity
ST segment elevation — 54 percent sensitivity
 Abnormal Q waves — 31 percent sensitivity
Initial positivity in V1 with a Q wave in V6 — 20 percent
sensitivity but 100 percent specificity for anteroseptal MI.
Cabrera's sign — 27 percent sensitivity overall, 47 percent
for anteroseptal MI

15. In addition to difficulties in ECG interpretation,
approximately one-half of patients with LBBB and an
acute MI do not have chest pain. These patients are much
less likely to receive appropriate medical therapy (eg,
aspirin, beta blockers) or reperfusion therapy than LBBB
patients with chest pain.

16. Serial ECGs, Enzymes help in diagnosis
American College of Cardiology/American Heart
Association guidelines recommend reperfusion therapy
for all patients with LBBB whose history suggests acute
myocardial infarction.

17. Thank you