A True Emergency
Memories of the VII Nursing Updates Symposium
Doris Maldonado Ardila*
* Nurse Specialist in Cardiorespiratory Javeriana University.
Adult UCI Children’s Cardio Foundation.
Introduction
Coronary heart disease, acute myocardial infarction (AMI), continues to be the leading cause of morbidity and mortality in the adult population; In Colombia it would be, if it were not for the phenomenon of violence that currently occupies first place. In developed countries, mortality from heart attacks has decreased significantly, due to improvements in prevention and treatment.
Diagnosis of AMI
The initial diagnosis of acute myocardial infarction is usually based on a history of ischemic chest pain and early electrocardiographic changes. The diagnosis is later confirmed by either an elevation of serum enzymes and/or typical evolution of electrocardiographic changes. The presence of two of the three typical characteristics of the infarct allows the subsequent classification, size and location of the infarct. Within the first 24 hours of diagnosis, the patient with typical pain should be limited to naming it as a heart attack with or without ST elevation, since this point determines what type of treatment should be implemented. If it is an infarction with ST elevation, the most appropriate reperfusion therapy for the case must be immediately chosen.
Differential Diagnosis of Chest Pain
The following cardiac causes of chest pain should be included in the differential diagnosis table:
• Severe aortic stenosis
• Obstructive hypertrophic cardiomyopathy
• Syndrome
• Microvascular angina
• Pericarditis
• Dissection of the aorta
Non-cardiac causes of chest pain:
Pulmonary and thoracic
• Pleuritis
• Pneumonia
• Laryngotracheitis
• Bronchitis
• Mediastinitis
• Pulmonary embolism
• Severe hypoxia
• Pulmonary hypertension
• Mediastinal emphysema
Gastrointestinal
• Esophageal reflux
• Esophageal spasm
• Peptic ulcer
• Acute pancreatitis
• Bile duct diseases
• Musculoskeletal
• Degenerative joint disease involving the cervicodorsal spine
• Costochondritis
• Scalene syndromes
• Intercostal spasm
• Subacromian bursitis
Others
• Chest wall lesions, tumors, herpes zoster
• Anxiety states or panic disorders.
Electrocardiographic Diagnosis of AMI
In the spectrum of acute coronary syndromes (Q wave infarction, non-Q infarction), the surface electrocardiogram after the clinical history should be considered the most important diagnostic instrument due to its wide availability, low cost and its high predictive value in the Emergency study in the patient with suspected acute myocardial infarction. The behavior of the ST segment and the appearance or not of the Q wave are of great diagnostic, therapeutic and prognostic importance in these patients.
In acute myocardial infarction the cardinal objective is to consider reperfusion therapy as soon as possible. Currently, the electrocardiogram is considered a fundamental pillar to decide the use of fibrinolytic substances in a patient with acute ischemic syndrome because clinical studies have shown great benefit in infarcts with ST segment elevation with Q wave development and no benefit or harm even in cases of ST segment depression or exclusive changes in the T wave (unstable angina or non-Q AMI).
Patients with acute myocardial infarction and new left bundle branch block are also candidates for reperfusion therapy. Right bundle branch block does not present diagnostic difficulties for AMI. On the other hand, left bundle branch block presents some difficulties but some guidelines are useful. Thrombolytic therapy should be applied during the first 6-12 hours after the infarction has occurred.
The acute evolutionary phase of myocardial infarction can be divided into hyperacute, acute and subacute changes.
1. Hyperacute changes: the earliest electrocardiographic signs occur on the ST segment and the T wave.
2. Acute changes: the most specific signs of an acute infarction correspond to elevation of the ST segment in the leads located in front of the infarct area. Changes that are traditionally called reciprocal.
3. Subacute changes: ST segment elevation remains for a few days, becoming isoelectric earlier in infarcts on the inferior face and persisting longer on the anterior face.
Location of AMI
Anterior infarction: determined according to the lead of the electrocardiogram where ST elevation is seen.
Electrocardiography and its angiographic and prognostic correlation: the GUSTO study defined five admission electrocardiographic patterns that correlated with clinical presentation, coronary anatomy, and prognosis.
The first three components correspond to the anterior descending artery (ADA) and/or its collaterals.
Category I: proximal occlusion of the LAD before or in the first septal perforator. ST segment elevation: V1-V6, DI and AVL. It is accompanied by bundle branch block or anterosuperior fascicular block, bifascicular block (RBBB + BFAS) or Mobitz II second degree AV block (All are possible).
Cardiogenic shock or pump failure are common. Mortality at 30 days is 19.6% and at one year is 25.6%.
Category II: occlusion in the middle of the proximal LAD, on a long but distal diagonal, to the first septal perforator. The EKG may be similar to that of the patient in category I but there is no intraventricular conduction disorder. Cardiogenic shock is less common because the proximal portion of the ventricular septum is not involved. However, heart failure can occur and ventricular aneurysm complications are common. Mortality at 30 days is 9.2% and at one year is 12.4%.
Category III: distal occlusion in the LAD or occlusion in the diagonal (occlusion distal to a long diagonal or the diagonal itself), ST elevation in V1-V4 or D1 AVL, V5, V6. Mortality at 30 days is 6.8% and at one year is 10.2%.
Category IV: patients with medium to large acute inferior myocardial infarction. It is a subgroup that is heterogeneous, representing a spectrum that includes, in addition to the inferior region, the posterior, lateral and right ventricle regions.
The dominant right coronary artery is responsible for supplying all of these territories such that its proximal occlusion can result in a large and potentially fatal event. The EKG shows ST segment elevation in DII, DIII, AVF and additional changes in V5 and V6 (lateral) and/or V1 or V3 R, V4 R (Right Ventricle) or R/S 1 in V1, V2 (posterior) with or without ST depression. The larger the inferior MI, the more shunts will be involved. In all patients with inferior MR, records of right leads should be obtained; ST segment elevation >1mm in V3 R or V4 R is quite specific for involvement of the right ventricle, sensitivity is suboptimal and signs of systemic venous congestion should be looked for and if in doubt, an echocardiogram should be performed. In these cases there may be pump failure, or cardiogenic shock due to RV compromise or the development of VSD due to extensive septal necrosis. There may be hypervagotonia with bradycardia and hypertension that responds to atropine, Mobitz I second degree AV block, intranodal third degree AV block. In small lower face infarction, mortality at 30 days is 6.4% and at one year it is 8.4%.
Category V: small infarction of the lower face. Distal occlusion of the right or circumflex coronary artery. The EKG with ST segment elevation in only DII, DIII and AVF (at least 2). Mortality at 30 days is 4.5% and at one year it is 6.7%.
An electrocardiogram is recommended for all patients with symptoms suggestive of chest pain of cardiac ischemic origin, and it can be repeated even every 15-30 minutes according to the clinical weight of the history if the aim is to make or clarify the initial diagnosis.
During follow-up, it is recommended to perform an electrocardiogram in patients with rhythm alterations, post-reperfusion or every 6 to 8 hours during the first 24 hours and then daily to monitor changes.
Other electrocardiographic alterations during acute myocardial infarction will depend on conduction alterations. Left anterior hemiblock, left posterior hemiblock, right bundle branch block, complete left bundle branch block may appear. Right bundle branch block and left anterior hemiblock are the most common.
Atrioventricular conduction disorders are common in inferior infarction, and sinus bradycardia and AV block of I, II and III degree may be found.