Miquel Fiol‐Sala’s research while affiliated with Hospital Universitari Son Espases and other places

Interatrial blocks like other types of block may be of first degree or partial second degree, also named transient atrial block or atrial aberrancy, and third degree or advanced. In first degree, partial interatrial block (P-IAB), the electrical impulse is conducted to the left atrium, through the Bachmann’s region, but with delay. The ECG shows a P-wave ≥ 120 ms. In third-degree, advanced interatrial block (A-IAB), the electrical impulse is blocked in the upper part of the interatrial septum (Bachmann region); the breakthrough to LA has to be performed retrogradely from the AV junction zone. This explains the p ± in leads II, III and aVF. In typical cases of A-IAB, the P-wave morphology is biphasic (±) in leads II, III and aVF, because the left atrium is activated retrogradely and, therefore, the last part of the atrial activation falls in the negative hemifield of leads II, III and aVF. Recently, some atypical cases of A-IAB have been described. The presence of A-IAB is a risk factor for atrial fibrillation, stroke, dementia, and premature death.

The heart is a pump that sends blood to every organ in the human body. There are various methods used to record the electrical activity of the heart. The best known method is electrocardiography. An alternative method, rarely used in clinical practice today but very useful in understanding electrocardiogram (ECG) curves and therefore helpful in learning about ECGs, is vectorcardiography. The vectorcardiogram (VCG) is the result of the joined heads of the multiple vectors that are formed during the consecutive processes of depolarization and repolarization of the heart. Although ECG–VCG correlation is used in this book to explain how the different ECG patterns appear, the recording of vectorcardiographic loops for diagnostic purposes is rarely used in clinical practice at present. Many details provided by amplified VCG loops can also be obtained from surface ECGs through amplification of the ECG waves, if necessary.

Premature supraventricular complexes are premature complexes of supraventricular origin. Premature supraventricular complexes that have an extremely variable coupling interval are called parasystoles, and the most common mechanism is increased automatism. When supraventricular tachyarrhythmia runs occur, sometimes the first complex of the run shows an aberrant morphology which is a result of the Gouaux‐Ashman phenomenon. In the electrocardiogram (ECG), sinus tachycardia presents as an increase in heart rate that occurs progressively in the majority of cases, and persists over a certain amount of time, with certain changes, until the triggering stimulus disappears. The prognosis depends on the heart rate, the underlying pathology, and the impact over LV function and whether the tachycardias are paroxysmal or incessant. The ECG is often normal in paroxysmal atrial fibrillation and has other various ECG signs according to the underlying heart disease in case of permanent atrial fibrillation.

The interpretation of an electrocardiogram (ECG) should be systematically approached in a sequential way. This chapter discusses the normal value of each parameter at different ages and other ECG variants to ensure a successful ECG interpretation. Sinus rhythm may be concealed due to extensive atrial fibrosis in the presence of large atria, particularly in valvular diseases that do not initiate measurable potentials on the surface ECG. However, in some leads, often in V1, a small P wave may be seen. The true PR interval is obtained by measuring from the onset of the P wave to the onset of the QRS complex in any of the three leads. The PR segment is the distance between the end of P wave and QRS. The abnormalities of repolarization encompass not only the U wave alterations already mentioned, but especially the T wave disturbances and the abnormal deviations of the ST segment.

The ventricular conduction system is formed by the right and left bundle branches, their respective divisions and their interconnected Purkinje networks. In peripheral right bundle branch block (RBBB), right ventricular activation is also delayed, but the activation sequence is different because the transseptal component is missing. The association of RBBB with right ventricular enlargement produces a right‐deviated AQRS that has to be differentiated from advanced RBBB with inferoposterior hemiblock. Activation commences at the base of the anterior papillary muscle of the right ventricle, and then transseptally depolarizes the septum anteriorly too posteriorly before depolarizing the free left ventricular wall. Patients with left bundle branch block present with an abnormal depolarization of the left ventricle that has hemodynamic consequences and may induce an impairment of left ventricular function and even heart failure. The detention of the impulse in the superoanterior fascicle modifies the sequence of left ventricular depolarization and, consequently, the QRS loop.

This chapter reviews the different electrocardiogram (ECG) characteristics in non‐cardiac processes and other situations, which are sometimes striking. Cerebrovascular accidents, and particularly subarachnoid hemorrhage, frequently show general repolarization abnormalities of the T wave, which can be highly negative or highly positive but are generally wide, and with long QT and mirror patterns in frontal plane leads. Numerous lung diseases may cause involvement of the right chambers both: in the acute setting, acute cor pulmonale due to pulmonary embolism or acute decompensation of chronic obstructive pulmonary disease; and in the chronic phase, emphysema and chronic cor pulmonale. The chapter comments on the global ECG changes that may be found in athletes in surface ECG, divided into frequent ECG findings that may be training related and uncommon ECG findings that are not training related. Many drugs alter the ECG morphology. Alcoholics with heart failure exhibit typical alterations frequently found in dilated cardiomyopathies of other etiologies.

The ECG waves are recorded in different forms according to the location of the explorer electrode. The morphology of the ECG is determined by the location at which the lead is recorded. ECG devices record the electrical activity of the heart through both frontal and horizontal plane leads. There are six frontal plane leads and six horizontal plane leads (V1–V6). This chapter explains some aspects of the ECG–VCG correlation using Burger's triangle. There is an increased interest in revising the standard presentation of the frontal plane ECG leads by changing the lead aVR location. Vectorcardiographic loops originate in the frontal or horizontal plane leads with different ECG morphologies, with QRS complexes more or less wide, and with positive, negative, or diphasic deflections in accordance with their projections in the respective positive and negative hemifield. The chapter focuses on the recording process and the technical errors that may occur during this process.

The assessment of 12‐lead electrocardiograms (ECGs) requires the detection of any abnormalities. If present, the diagnostic value and possible clinical implications of these abnormalities must be determined. This chapter explains how a thorough study of the ECG waves and intervals, as well as knowing their normal values, allows not only for the identification of whether an ECG tracing is within a normal range but also for the diagnosis of an ECG abnormality and understanding of its clinical implications. It describes especially the abnormalities of different parameters. It subsequently discusses the different cardiac intervals (PR and QT) and waves’ (P, QRS, ST–T–U) abnormalities. The chapter also comments on the presence of repolarization changes in various clinical settings. It discusses the importance of history taking, blood tests, and especially the surface ECG, bedside diagnostic methods that may be used in any medical center and usually are sufficient to arrive at a diagnosis.

This chapter discusses the heart diseases that are deemed to be due to inherited changes. Hypertrophic cardiomyopathy (HCM) is usually a familial disease of genetic origin, characterized by alterations in proteins of the myocardial cells leading to myocardial fiber disarray, hypertrophy of the heart, and an increased incidence of sudden death. In contrast to what is observed in the inherited long QT syndrome, in HCM, it is not possible to predict the different mutations based on the electrocardiogram changes, and vice versa, except for some types of predominantly apical HCM. Patients with HCM present with progressive dyspnea, especially after 40‐50 years, due to diastolic dysfunction. Implantable cardioverter defibrillator therapy is considered the best treatment option, particularly in patients with a history of sustained ventricular tachycardia/ventricular fibrillation, patients with extensive left ventricular involvement, and those with a history of syncope.