maximal spatial St-vector patterns in patients with acute anterior myocardial infarction

W. Carson, Y. Z. Tseng
Cardiovascular Division, Department of Internal Medicine,
National Taiwan University Hospital, 
No. 7, Chung-Shan South Road, Taipei, Taiwan 100

Abstract:  One hundred and forty-one consecutive patients with suspected acute myocardial infarctions were studied. On admission to the Coronary Care Unit through the Emergency Service, each patient was given electrocardiographic and Frank lead vectorcardiographic examinations. Thirty-seven patients continuously met the vectorcardiographic QRS-loop criteria for anterior myocardial infarction. There were 29 males and eight females. Their ages ranged from 38 to 85; mean + SD was 60.57 + 9.67 yrs. In the acute localized anterior myocardial infarction subgroup, the direction of the maximal spatial ST-vector pointed to one of the following octants: (1) right-anterior-inferior or (2) right-anterior-superior or (3) left-anterior-superior. In both the acute antero-lateral or extensive anterior myocardial infarction subgroups, the direction of the maximal spatial ST-vector pointed to one of the following octants: (1) left-anterior-superior  or (2) left-anterior-inferior  or (3) right-anterior-superior. The directions  were the same as the types of initial activity of the normal depolarization process of the interventricular septum revealed by the intracardiac mapping in dogs or initial spatial QRS patterns in male pilots. This study further confirmed that in the 3-dimensional view, there are generally three types of the maximal spatial ST-vector concealed in patients with first acute anterior myocardial infarctions.

INTRODUCTION

Patterns of the maximal spatial ST vector in patients with acute right ventricular infarction [1] and acute strict inferior myocardial infarction [2] in the Emergency Vectorcardiography had been reported. Patterns of the maximal spatial ST vector in patients with acute anteroseptal myocardial infarction had also been documented [3]. This research is intended to investigate patterns of the maximal spatial ST vector in patients with acute localized anterior, antero-lateral, and extensive anterior myocardial infarctions.

METHODS

One hundred and forty-one consecutive patients with suspected acute myocardial infarctions indicated by chest pain, compression and/or cold sweating, followed by serial electrocardiographic changes and serial serum enzyme changes were studied. Patients with a history of chronic lung disease, pulmonary embolism, non-ischaemic heart disease, or previous myocardial infarctions were excluded. On admission to the Coronary Care Unit through the Emergency Service, each patient was given electrocardiographic and vectorcardiographic examinations, which were repeated at intervals of 24hrs if the patients’ conditions were conducive to do so. All the electrocardiograms and vectorcardiograms were recorded by the first author (W.C.) according to  orthodox methods of medical research [4], and read by the other author (Y.T.) without any knowledge of the patients. 

A Sanborn vector programmer model 1507A and a Sanborn visoscope model 780-6A were used for vectorcardiogram. Vectorcardiograms were photographed through a Sanborn oscilloscope camera model 197A with Polaroid film. The vectorcardiograms in the three projection planes were recorded in the supine position using the Frank lead reference system. In addition to the complete recording of the P-QRS-T loop complex, highly magnified spot films of the T loop were taken for detailed analysis.

The vectorcardiographic QRS-loop diagnostic criteria for localized anterior, antero-lateral, or extensive anterior myocardial infarctions were according to the literature [5,6]

RESULTS

Thirty-seven patients continuously met the vectorcardiographic QRS-loop criteria for anterior myocardial infarction during the acute phase follow-up period except when sudden death ensued or the patient was too ill.  All the patients had their initial  vectorcardiographic tracing within 24 hours of first symptom.  There were 29 males and eight females. Their age ranged between 38 and 85; mean + SD was 60.57 + 9.67 yrs.

Localized anterior myocardial infarction

A total of 32 emergency vectorcardiograms were recorded for the 10 patients. In the first tracing, the magnitude of the maximal ST-vector ranged from 0.15 mV to 0.9 mV in the Horizontal plane. The direction of the maximal spatial ST-vector pointed to one of the following octants: (1) right-anterior-inferior (four patients) or (2) right-anterior-superior (five patients) or (3) left-anterior-superior (one patient).  In the serial follow-up tracings, changes in the direction of the maximal ST-vector were noted. One patient changed from right-anterior-inferior octant to left-anterior-inferior octant.

Antero-lateral myocardial infarction

A total of five patients had 14 emergency vectorcardiographic tracings. The magnitude of the maximal ST-vector in the first tracing ranged from 0.1 mV to 0.5 mV in the Horizontal plane. The direction of the maximal spatial ST-vector pointed to one of the following octants: (1) left-anterior-superior (two patients) or (2) left-anterior-inferior (two patients) or (3) right-anterior-superior (one patient). Changes in the direction of the maximal ST-vector were noted in the serial follow-up tracings. One patient changed from left-anterior-superior octant to left-anterior-inferior octant, another from left-anterior-inferior to left-anterior-superior octant.

Extensive anterior myocardial infarction

A total of 77 emergency vectorcardiograms were recorded for the 22 patients. In the first tracing, the magnitude of the maximal ST-vector ranged from 0.3 mV to 0.875 mV in the Horizontal plane. The direction of the maximal spatial ST-vector pointed to one of the following octants: (1) left-anterior-inferior (12 patients) or (2) left-anterior-superior (seven patients) or (3) right-anterior-superior (three patients).  In the serial follow-up tracings, changes in the direction of the maximal ST-vector were noted. Three patients changed from  left-anterior-inferior octant to left-anterior-superior octant, two from left-anterior-superior octant to left-anterior-inferior octant and one from right-anterior-superior octant to left-anterior-superior octant.

DISCUSSION

As expected, the  initial magnitude of the maximal ST-vector in the vectorcardiographic Horizontal plane in patients with acute extensive anterior myocardial infarction was larger than the acute localized anterior or acute antero-lateral myocardial infarction. This is in accordance with the concept that the bigger the injury to the myocardium, the larger the maximal ST-vector.

Interestingly, the directions of the maximal spatial ST-vector in patients with acute antero-lateral or acute extensive anterior myocardial infarction were the same as our previously reported acute anteroseptal myocardial infarction in the literature [3]. The directions  were the same as the types of initial activity of the normal depolarization process of the interventricular septum revealed by the intracardiac mapping in dogs [7] or initial spatial QRS patterns in male pilots [8]. Further, two types of the maximal spatial ST-vector in patients with acute localized anterior myocardial infarctions also support with this. The right-anterior-inferior maximal spatial ST-vector in patients with acute localized anterior myocardial infarctions also coincides with one pattern of initial spatial QRS patterns in male pilots. This study further confirmed that in the 3-dimensional view, there are three types of the maximal spatial ST-vector concealed in patients with first acute anterior myocardial infarctions.

The evidence of the results demonstrates that the maximal spatial ST-vector in an anterior myocardial infarction can still change its direction in some of our patients. The results of this research will bring the section of an acute anterior myocardial infarction of the Emergency Vectorcardiography [9] up to date. Further, the results will be integrated with the algorithm of the 3-D animation software [10] under construction.

REFERENCES

[1] W. Carson, Y.Z. Tseng, C.D. Tseng, et al.. “Vectorcardiographic criteria for acute right ventricular infarction” Eur Heart J, vol. 9, pp. 955-961, 1988.

[2] W. Carson, N. Soper. “Patterns of the maximal spatial ST vector in patients with acute strict inferior myocardial infarction” in Proceedings of the XXVIII International Congress on Electrocardiology, 2002,pp.(in press) .

[3] W. Carson, Y. Z. Tseng. “Maximal spatial ST-vector patterns in patients with acute anteroseptal myocardial infarction,” Int J Cardiol, vol.43, pp. 165-173, 1994.

[4] K.I. Shine. Cardiology: a transatlantic view (1). Br Heart J, vol. 58, pp. 552-555, 1987.

[5] H.H. Friedman. Diagnostic Electrocardiography and Vectorcardiography. New York: Mcgraw-Hill Book Co., 1985.

[6] T.C. Chou, R.A. Helm, S. Kaplan. Clinical Vectorcardiography. New York, Grune & Stratton Inc., 1974

[7] N.S. Amer, J.H. Stuckey, B. F. Hoffman, et al. “ Activation of the interventricular septal myocardium studied during cardiopulmonary bypass. Am Heart J, vol. 58, pp. 224-237, 1960.

[8] W. Carson, B.L. Ho. “Initial spatial QRS patterns in pilots – a preliminary report.” in Proceedings of the XXIII International Congress on Electrocardiology, 1996, pp.671-674.

[9]  W. Carson. Emergency Vectorcardiography.  London,  1998. (www.castonenterprises.com)

[10] W. Carson, “3-D animation software in emergency vectorcardiography and a palm-like device for the timed vectorcardiogram: a preliminary developing project” in Proceedings of the XXVIII International Congress on Electrocardiology, 2002,pp.(in press).