ABC | Volume 115, Nº1, Suplement, July 2020

Case Report Transient Prominent Anterior QRS Forces in Acute Left Main Coronary Artery Subocclusion: Transient Left Septal Fascicular Block Andrés Ricardo Pérez-Riera, 1 Raimundo Barbosa-Barros, 2 Rodrigo Daminello Raimundo, 1 Luiz Carlos de Abreu, 1 Marcos Célio de Almeida, 3 Kjell Nikus 4 Centro Universitario Saúde ABC, 1 Santo André, SP - Brazil Hospital de Messejana Dr. Carlos Alberto Studart Gomes, 2 Fortaleza, CE - Brazil Universidade de Brasília - Instituto de Biologia-Genética e Morfologia, 3 Brasilia, DF - Brazil Heart Center, Tampere University Hospital and Faculty of Medicine and Life Sciences, 4 Tampere – Finland Introduction The left main coronary artery (LMCA) originates from the left sinus of Valsalva, passes between the main pulmonary artery and the left atrial appendage before entering the coronary sulcus and bifurcates into the left anterior descending (LAD) and the left circumflex (LCX) coronary arteries. In most individuals, the LMCA supplies ≈75% of the left ventricle (LV). 1 Significant stenosis, which may lead to stable angina and/or acute coronary syndrome, places the patient at risk of life-threatening acute left ventricular failure and malignant arrhythmias. Patient prognosis of LMCA disease can be improved with coronary artery bypass grafting (CABG). With technical improvement and effective anti-thrombotic medication, percutaneous coronary intervention (PCI) has evolved as an alternative therapeutic modality. In patients with severe LMCA disease having low to intermediate anatomic complexity, both CABG and PCI are effective methods of revascularization with comparable long-term rates of death, myocardial infarction, and stroke. 2 Patients most suitable for LMCA stenting are those with isolated ostial/ mid LMCA disease, protected LMCA disease and those who undergo an elective stenting procedure. In a recent study, 8% mortality and 8% target lesion revascularization rate during one-year follow-up was reported. 3 Case description A 72-year-old Caucasian male presented at the emergency department complaining of prolonged oppressive chest pain at rest since ≈1 hour associated with cold diaphoresis and respiratory distress. He had a history of type 2 diabetes mellitus and dyslipidemia had been detected four years before. Two months earlier, he had oppressive precordial pain on moderate exertion, which disappeared rapidly after rest. Figure 1 shows the ECG at admission and Figure 2-A an ECG performed 30 days before. The coronary angiography indicated subocclusion (91-99% diameter stenosis) in the middle portion of the LMCA (Figure 2-B). CABG was immediately proposed, but the patient refused. He successfully underwent PCI with DES implantation without in-hospital complications. During the 6-month follow-up no target lesion revascularization was required on the LMCA. The patient remained asymptomatic even at efforts and several follow-up ECGs were normal. Discussion An ECG performed due to stable angina symptoms 30 days before the hospital admission, showed a pattern suggestive of LMCA disease and possibly some degree of LSFB. 4,5 These “minimal findings” in the scenario of stable angina should alert the clinician about the possibility of severe myocardial ischemia in patients without a logical explanation for the ECG findings, such as left ventricular hypertrophy with strain in structural heart disease. Both ECG features are evident, with more pronounced ischemic findings in the ECG performed at admission when the patient had acute coronary syndrome. Several successive manuscripts from our group and others have shown that a large proportion of cases with transient left septal fascicular block (LSFB), manifested by prominent anterior QRS forces, is caused by critical proximal obstruction of the LAD before its first septal perforator branch. 6-9 As the LAD is a continuation of the LMCA, significant LMCA obstruction, may lead to ischemia in themid-portion and apical territory of the left ventricle, where the left septal fascicle runs, thereby causing LSFB. In the presence of LSFB, the sequence of ventricular activation begins only at two points: The base of the anterolateral papillary muscle (ALPM) of the mitral valve dependent on the left anterior fascicle (LAF) in the anterior paraseptal wall, just below the ALPM attachment (1 AM vector); The base of the posteromedial papillary muscle of the mitral valve (PMPM) dependent on the left posterior fascicle (LPF). It is located in the posterior paraseptal wall, at about one-third of the distance from the apex to the base (posteroinferior vector – 1 PI ). These two initial vectors have opposite directions, and they cancel each other with minimal predominance of the 1 PI vector directed backward (Figure 3). This explains the absence of the normal initial convexity to the right of the QRS loop in the horizontal plane, dependent on the 1 AM septal vector (or Mailing Address: Andrés Ricardo Pérez-Riera • Rua Nicolau Barreto, 258. Postal Code 04583-000, São Paulo, SP – Brazil E-mail: riera@uol.com.br, arperezriera@gmail.com Manuscript received November 18, 2018, revised manuscript May 30, 2019, accepted August 18, 2019 Keywords Coronary Occlusion; Truncus Arterious; Acute Coronary Syndrome; Fibrinolytic Agents; Percutaneous Coronary Intervention; Angina, Stable; Electrocardiography/methods. DOI: https://doi.org/10.36660/abc.20180363 1