Electrocardiographic findings during balloon angioplasty of the left circumflex coronary artery - influence of location of the ischemic segments with respect to the obtuse margin of the left ventricle

Why do we keep missing left circumflex artery myocardial infarctions?

BACKGROUND

Diagnosis of left circumflex artery (LCx) myocardial infarctions via 12‑lead electrocardiogram (ECG) has posed a challenge to healthcare professionals for many years.

METHODS AND RESULTS

A retrospective observational study was performed to analyze patients admitted with myocardial infarction. The study used electronic medical records and specific ICD-10 codes to identify eligible patients, resulting in 2032 encounters. After independent adjudication of cardiac biomarkers, coronary angiography, and electrocardiographic changes, a final patient population of 58 encounters with acute occlusion myocardial infarction (OMI) with a culprit LCx lesion was established. OMI was defined as a lesion with either thrombolysis in myocardial infarction flow (TIMI) 0-2 or TIMI 3 with Troponin I > 1 ng/mL (Reference range 0.00-0.03 ng/mL). ECGs of these patients were then independently evaluated and grouped into 8 different classifications based on the presence or absence of ST elevation and/or depression in corresponding leads. ECG patterns and anatomical characteristics (proximal or distal to the first obtuse marginal artery) of the LCx lesions were then correlated. The appropriateness of triage and delay in reperfusion therapy were also assessed. Those with a left dominant or codominant circulation, and with LCx lesions proximal to the first obtuse marginal artery, were more likely to present with no or subtle ST-segment changes that led to delays in reperfusion therapy.

CONCLUSIONS

Patients with left or codominant coronary artery circulation, with OMI proximal to the first obtuse marginal artery, may be less likely to have "classic" findings of ST-segment elevation on ECG due to cancellation forces in the limb leads.

Early ischemic ST-segment and T-wave changes during balloon angioplasty

BACKGROUND

Acute coronary occlusion results in increased T-wave amplitude and ST-segment elevation in the ECG leads facing the ischemic region.

MATERIAL AND METHODS

We performed continuous ECG recording in 34 patients during balloon occlusion of the left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA). Delta (Δ) ST and ΔT amplitudes were calculated by subtracting the preinflation values from the values measured during balloon inflation.

RESULTS

Occlusion of the LAD resulted in greater increase in the amplitude of the T wave than of the ST segment in lead V2 (ΔT +3.4 mm, inter-quartile range [IQR] 1-6 mm; ΔST +1.4 mm, 0.5-3 mm). During RCA occlusion, ΔST and ΔT didn't differ significantly. LCx occlusion resulted in significant differences between ΔST and ΔT in all leads, except aVF and V3-V4. In two patients (LCx), we observed a biphasic ST-T response: an initial negative change of the T-wave amplitude was followed by a positive change in leads V1-V2. In leads II, III, aVF and V4-V6, there was an initial positive change, followed by a final negative change towards the end of the occlusion.

CONCLUSION

Continuous 12‑lead ECG recording during balloon occlusion of the LCx resulted in significant differences between the ΔST and ΔT values in all leads except aVF and V3-V4. LAD and RCA occlusion resulted in less evident differences between the ST-segment and T-wave changes. A change in polarity of T-wave changes during balloon occlusion (initial negative and final positive change, or vice versa) proved to be a rare finding.

Clinical and Prognostic Value of the Electrocardiogram in Patients With Acute Occlusion of the Left Circumflex Coronary Artery

The utility of the electrocardiogram (ECG) in patients with acute left circumflex (LC) coronary occlusion is not established. This study aimed at determining the clinical, angiographic, and prognostic characteristics associated with the different patterns of ST-segment changes in patients with LC occlusion. A cohort of 314 patients with LC occlusion was categorized according to the admission ECG: (1) ST-segment elevation (ST-E, n=208), (2) isolated ST-segment depression in precordial leads (ST-D, n=62), and (3) negligible ST-segment changes (No-ST, n=44). Clinical variables, coronary angiography, and 30-day major adverse cardiac event (MACE) (in-hospital ventricular fibrillation, 1-month mortality, or heart failure) were compared among the three groups. As compared with No-ST, patients with ST-E or ST-D presented more advanced Killip class, higher troponin peak, lower LV ejection fraction, and were independently associated with MACE (odds ratio 5.43, 95% confidence interval 1.09 to 27.20 and odds ratio 3.39, 95% confidence interval 0.66 to 17.50, respectively). Patients with ST-D were tardily reperfused, had more often mitral regurgitation (23.1% vs 9.3% in ST-E and 3.3% in No-ST, p=0.03), and presented ST-segment elevation in leads V7 to V9 in 12 of 16 cases with available recordings. Culprit proximal LC predominated in ST-D (41.9%), distal LC in ST-E (42.8%), and obtuse marginal in No-ST (59.1%) (all p<0.01). The No-ST had smaller coronary vessels and more collaterals. In conclusion, the three ST-segment patterns of LC occlusion identify patients with different clinical, angiographic, and prognostic characteristics. Patients with ST-depression pattern require a prompt reperfusion therapy and could be better recognized by recording leads V7 to V9.