This chapter deals with the most important electrocardiographic abnormalities present in heart diseases other than ischemic heart disease (see Chapter 20) and inherited heart diseases (see Chapter 21). Currently, the incidence of valvular heart diseases of rheumatic origin in developed countries is very rare and usually only found in immigrant populations. However, many cases of adults with rheumatic valvular heart disease acquired several decades ago still exist. The most frequent causes of valvular heart diseases are aortic stenosis and mitral regurgitation. Aortic stenosis is mainly due to degenerative calcification in the elderly but can be seen in younger patients with bicuspid aortic valve. Mitral regurgitation is mainly related with mitral valve prolapse and with dilated cardiomyopathy. The presence of left or right ventricular enlargement usually indicates that the disease is severe. The most frequent ECG findings and their clinical significance are explained below. Mitral stenosis typically presents with a P wave ± in V1 and a wide and biphasic P wave in other leads, especially I and II, as an expression of left atrial enlargement (P mitrale) (see Figure 9.35). We have to remember that for the evaluation of the P wave in V1, it is essential that the V1 electrode is correctly located. Throughout the natural evolution of mitral stenosis, atrial fibrillation is very common; the more abnormal the P wave, the more likely the appearance of this arrhythmia. In this sense, the presence of a P wave of ≥0.12 and ± in II, III, and aVF is a very specific marker of paroxysmal supraventricular arrhythmias in the future (Bayés de Luna et al. 1989). In our experience, nearly every patient with valvular heart disease who presents this kind of interatrial block has presented paroxysmal arrhythmia, atrial fibrillation or flutter especially atypical flutter, within the first year (see Chapter 9). The presence of ECG signs of right ventricular enlargement (evident R wave ≥3 mm in V1) suggests pulmonary hypertension (see Figure 10.4). A ratio QRS voltage in V2/QRS voltage in V1 >5 suggests right atrial and ventricular enlargement (see Figure 9.7). ECG signs of left ventricular enlargement suggest the possibility of other associated lesions (mitral regurgitation and/or associated aortic valve disease). Non‐severe mitral regurgitation, alone or associated with mitral stenosis, may alter the ECG slightly. When significant regurgitation is found, however, ECG signs of left ventricular enlargement associated with an abnormal P wave or atrial fibrillation are usually observed. In mitral valve prolapse, repolarization abnormalities are frequently found in II, III, aVF, and left precordial leads. Atrial arrhythmias are common, especially frequent premature atrial complexes and atrial fibrillation, and ventricular arrhythmias might be seen (Figure 22.1), especially when mitral prolapse is severe, in which case the ECG is rarely normal. Tricuspid regurgitation secondary to mitral stenosis with pulmonary hypertension usually shows in the ECG signs of right chamber enlargement (see Figures 10.34 and 10.35). Isolated aortic valve disease, except at advanced stages, is not typically accompanied by significant signs of left atrial enlargement or atrial fibrillation. Therefore, if these ECG signs are present in non‐advanced cases, associated mitral valve disease must be suspected. Figure 22.1 Bottom: A patient with mitral valve prolapse. Top: In the Holter recording, an ST‐segment depression is seen at rest (A) and increases with exercise (B). In the early stages of left ventricular enlargement, there is usually a pattern of qR morphology with positive T wave in left lateral leads, which is more evident with aortic regurgitation then with aortic stenosis (a deeper “q” wave and a taller T wave). This pattern has been considered (Cabrera and Mouroy 1952) a result of diastolic hemodynamic overload (see Chapter 10), but we now know that in advanced cases both aortic stenosis and aortic regurgitation generally show a similar morphology, known as “strain pattern” (see Figure 10.21) (somewhat depressed ST segment followed by a negative and asymmetric T wave). Although the ST segment/T wave pattern is similar in both cases, in aortic regurgitation, the R wave is often still preceded by a usually small Q wave, which usually decreases over time, whereas in aortic stenosis, QRS complex morphology tends to be a pure R wave (see Figure 10.21). Sometimes, a mixed pattern is seen, T wave more negative than usual and/or more symmetrical, or a more marked decrease of ST segment due to an added primary factor, such as associated ischemia or myocardial compromise or due to drug effects (see Figure 10.28). The so‐called pattern of diastolic overload is observed in the early stages of any type of ventricular enlargement due to aortic valve disease, but not in the ventricular enlargement of isolated aortic regurgitation. The “strain pattern,” named by Cabrera in 1956, is a pattern of systolic overload observed in more advanced stages of aortic valve disease, regardless of the predominance of stenosis or regurgitation. On the other hand, it has been proven that the presence or absence of a “q” wave in V5–V6 is more directly related to the degree of septal fibrosis (more fibrosis, less “q” wave) than the type of lesion (Bayés de Luna et al. 1983) (see Figures 10.22 and 10.23). The presence of clear signs of left ventricular enlargement with a “strain” pattern indicates a severe and long‐lasting aortic valve disease, is often correlated with the presence of symptoms, and is a marker of poor prognosis. Surgery is recommended in the presence of LV failure, syncope, or angina. However, it is not uncommon that patients with severe aortic stenosis with significant left ventricular enlargement have only discrete ECG abnormalities. This is not usually the case for patients with advanced aortic regurgitation. Patients with advanced aortic valvular disease frequently present with ventricular arrhythmias and intraventricular blocks and atrioventricular (AV) block (calcification of the aortic valve), even more than those with advanced mitral valve disease, but the latter more frequently present atrial fibrillation. The occurrence of new conduction abnormalities, including LBBB, has been reported to be the most frequent complication following transcatheter aortic valve implantation (TAVI) (Martinez‐Selles et al. 2015). These conduction disturbances are mainly seen in the first 48 hours after TAVI (Kooistra et al. 2020) and their reasons and clinical significance are yet to be fully delineated. Specific procedure and patient‐related factors may contribute to the development of LBBB and aberrant atrioventricular conduction following TAVI as well as its clinical consequences. There are three major functional types of cardiomyopathies: dilated, hypertrophic, and restrictive. Hypertrophic cardiomyopathy (HCM) is usually inherited. Cardiomyopathies of inherited origin are explained in Chapter 21. Acute inflammatory myocarditis is caused by diverse infectious agents (most commonly viruses) or agents of unknown origin. This section is focused on ECG abnormalities seen in the acute stage of idiopathic or viral myocarditis. Acute myocarditis may be severe, with signs of heart failure or even lethal evolution in a very short time, and may lead to dilated cardiomyopathy. However, the evolution is usually favorable and a restitutio ad integrum is often observed. It should be remembered that this state may appear isolated or as part of a generalized viral disease. In fact, many viral diseases, from the flu to hepatitis, show transient ECG abnormalities in 5–20% of cases. In the acute stage, sinus tachycardia, low‐voltage, and various supraventricular arrhythmias, such as atrial fibrillation that may be transient, and ventricular arrhythmias, especially ventricular premature complexes, are common. Advanced AV block is generally transient. Cases with progression to dilated cardiomyopathy may present an intraventricular conduction block. Often, the evolution is favorable but a right or left bundle branch block can persist. Also, repolarization abnormalities are frequently present, particularly flat or usually mild negative T waves, that may be deep or have a ± morphology, and/or an abnormal ST segment. These abnormalities are usually observed in many leads. The upsloping ST segment elevation is concave with respect to isoelectric line, at least in some leads (Figure 22.2). In some cases, differential diagnosis with ST‐segment elevation acute coronary syndrome (ACS) may be difficult. During the evolution of acute myocarditis, Q wave ECG, or even QS pattern, may be present. Usually, it is not very deep, and is transient. The difficulty in making a diagnosis increases due to the presence of precordial discomfort, especially in cases of perimyocarditis and increase in biomarkers. Thus, it may be necessary to perform coronary angiography, multislice computerized tomography (MSCT), and/or magnetic resonance imaging. The differential diagnosis is even more complicated with Tako‐Tsubo syndrome, (see Figure 20.44) (Tsuchihashi et al. 2001). The diagnosis of Tako‐Tsubo syndrome (see Chapter 20) is supported by: (i) marked upslope in the ST segment elevation; (ii) long QTc interval; (iii) “q” wave more frequently present, and less transient than in myocarditis; and (iv) deep negative T wave in the evolution (see Figures 13.11 and 20.4B). In clinical practice, the distinction is not easy to make and in some cases it is impossible without additional tests (see Chapter 20). However, persistent “q” wave is unusual in myocarditis, and the clinical presentation is frequently different. When the acute phase is over, the evolution is usually good, and in these cases the ECG remains mildly changed (usually slight changes in the T wave) or becomes normal. Unfortunately, some cases progress to dilated cardiomyopathy, even with a poor evolution in the short term. There are many etiologies for this infrequent type of cardiomyopathies (infiltrative including amyloid, sarcoid and Gaucher disease and non‐infiltrative usually idiopathic processes, storage diseases, including hemochromatosis, Fabry disease due to deficiency of the lisozomal enzyme a‐galactosidase A and all types of endomyocardial involvement). The hallmark is abnormal diastolic function usually with normal contractile function. Thus, restrictive cardiomyopathy bears some functional resemblance to constrictive pericarditis. The differential diagnosis is mandatory because of the potential surgical treatment of constrictive pericarditis. Figure 22.2 (A) Patient with acute myocarditis and ECG with signs of sinus tachycardia with RBBB plus LAHB and Q waves in many leads. After the acute phase (B), the Q waves and the LAHB disappear. In many leads, T wave inversion is still present. Observe the low voltage in both ECGs. Advanced restrictive cardiomyopathy may display some striking ECG patterns (Figure 22.3) including: (i) pseudo‐necrosis “q” wave; (ii) obvious repolarization abnormalities; and (iii) a P wave with a significant brisk negative component in V1 due to the significant left atrial enlargement frequently found; (iv) intraventricular conduction disorders; (v) prominent R in V1; and (vi) LVH with “strain.” All these parameters combined with echocardiography and clinical setting are useful for differential diagnosis (Hoigne et al. 2006) (Figure 22.3). Due to the presence of significant atrial dilation, atrial fibrillation is often present, even in young patients, and may be poorly tolerated. Heart transplant is often necessary but presents many problems due to frequent systemic involvement in infiltrative and storage diseases. Figure 22.3 (A) A patient with advanced restrictive cardiomyopathy. Note the presence of clear QRS abnormalities simulating lateral necrosis. Evident P wave signs of very important bi‐atrial enlargement are found in this type of a cardiomyopathy. (B) Patient of 56 years with cardiac amyloidosis that presents pathologic Q wave, low voltage, and abnormal repolarization (Hoigne et al. 2006). Dilated cardiomyopathy is the most frequent type of cardiomyopathy. It is a syndrome characterized by cardiac enlargement and impaired systolic and/or diastolic function of the left or both ventricles. It is considered idiopathic when the cause is a primary disease of heart muscle. Over time, the symptoms of congestive heart failure usually appear. Its importance is great because it has a high incidence, especially if we include all cases of hypertensive, valvular, or ischemic origin evolving to a clinical picture of heart failure in a similar way to the idiopathic cases of dilated cardiomyopathy. In a significant number of cases, the origin is unknown (idiopathic dilated cardiomyopathy). However, there is growing evidence that a relatively high number of idiopathic dilated cardiomyopathies are of genetic origin (around 30%). The etiology of dilated cardiomyopathy is commonly infectious, (viral), although in many cases there is no previous history of myocarditis. Furthermore, there are many causes of systemic, metabolic, or toxic origin, including alcohol and the administration of some chemotherapeutic drugs that can lead to a dilated cardiomyopathy. In South America, for example, Chagas cardiomyopathy continues to be a significant problem. It is caused by an acute myocarditis due to Trypanosoma cruzi, a flagellate protozoan present in jungle mammals and carried to humans via bites due to insects that typically dwell in the ceilings and walls of rural houses in Latin America (Mendoza and Acquatella 2003). In about 10–20% of cases, Chagas cardiomyopathy presents with different types of heart block and active arrhythmias and evolves to dilated cardiomyopathy with different degrees of heart failure. It is worth noting that in view of considerable existing immigration flows, there are certain to be many “silent” cases of Chagas cardiomyopathy, both in Europe and in the United States (Milei et al. 1992). Patients with dilated cardiomyopathy present with signs of left ventricular impairment that often evolves to heart failure with depressed (systolic) or preserved (diastolic) left ventricular function. For this reason, we will examine the ECG changes of dilated cardiomyopathy together with those of heart failure. Heart failure (HF) presents the most important challenge for cardiology in the twenty‐first century, because it represents the final path of all heart diseases. It is of particular significance to recall that hypertension is the most frequent cause of heart failure, along with ischemic heart disease. Heart failure occurs when the heart cannot efficiently pump blood to vital organs. The main symptom of heart failure is dyspnea, which is used to classify heart failure into different functional classes (NYHA). Today, it is known that heart failure develops via two pathophysiological mechanisms: heart failure with reduced ejection fraction, and heart failure with preserved ejection fraction. Mid‐range heart failure has also been introduced in Europe. B‐type natriuretic peptide (BNP) plasmatic levels in patients with dyspnea are very useful for the diagnosis. Heart failure with preserved ejection fraction might also have by congestion, acute pulmonary edema, and sudden death (Varela‐Román et al. 2002). It is quite rare that a patient with class III–IV heart failure does not present with ECG abnormalities. A normal ECG has a high negative predictive value (> 90%) and almost rules out the presence of significant left ventricular dysfunction (Remme and Swedberg 2001). In advanced cases of high output heart failure (e.g. beriberi), the ECG does not exhibit many abnormalities (Figure 22.4). In patients with hypertrophic cardiomyopathy, on the other hand, it has been proven that a relatively low voltage could be a marker of heart failure in the medium term (see Figure 21.5) (Ikeda et al. 1999). In hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia, the ECG may be normal in some few cases (see Chapter 21). However, a normal ECG may not rule out diastolic dysfunction in patients with clinical suspicion of HF. In these cases, it has been demonstrated that a longer QT interval may predict LV dysfunction (Wilcox et al. 2011). In patients with heart failure, the ECG may show signs of atrial and/or ventricular enlargement, intraventricular blocks (Escobar‐Robledo et al. 2018) and/or Q wave even in the absence of ischemic heart disease. The presence of low‐voltage QRS complex in the frontal plane is a characteristic of dilated cardiomyopathy, although high voltage is found in the right precordial leads (Figures 11.27, 11.30, and 11.31). Cases with advanced heart failure, especially due to the presence of anasarca, may present with a low voltage of QRS, T and also P waves (Madias 2008) (see pericarditis) that can disappear with the improvement of the disease (Figure 22.5) (Madias et al. 2001). QRS complexes are often notched and wide (with different degrees of left bundle branch block morphology). If advanced left bundle branch block (LBBB) is found, V3 voltage helps to differentiate idiopathic cardiomyopathy (with much higher QRS voltage) from ischemic cardiomyopathy (Figure 22.6) (Bayés‐Genís et al. 2003). This sign is probably more useful than repolarization abnormalities or even pathologic Q waves in differentiating between ischemic and idiopathic cardiomyopathy. The presence of advanced LBBB with very wide QRS complexes (≥170 ms) is an indicator of poor ventricular function (Das et al. 2001) and the presence of final R wave in aVR (QR) in advanced LBBB is a possible marker of RV dilation (Van Bommel et al. 2011) (see Chapter 11). The heart rate is usually increased and atrial fibrillation and ventricular arrhythmias are common. The association of LBBB and atrial fibrillation present in at least 5% of patients with congestive heart failure is a marker of poor prognosis (Baldasseroni et al. 2002; Vazquez et al. 2009). Figures 10.30, 11.27, 11.30, and 11.31 show typical examples of patients with idiopathic dilated cardiomyopathy in advanced stages of heart failure. It is estimated that approximately 40% of cardiovascular deaths reported in patients with heart failure are sudden, whereas the remaining deaths may be attributed to heart failure progression. The three‐year mortality rate in patients with heart failure (NYHA Classes II–III) is 20–30%. Half of these deaths can be attributed to sudden death (“a heart too good to die”). Cases of sudden death in patients with NYHA Classes II–III heart failure are mostly caused by ventricular arrhythmia (VT/ VF), whereas in NYHA Class IV patients, bradyarrhythmias play a more important role (Luu et al. 1989) (see Chapters 16 and 17). This may explain the inefficacy of antiarrhythmic drugs in preventing sudden death in Class IV patients. Figure 22.4 A 61‐year‐old patient with beriberi heart disease and heart failure who died in cardiogenic shock. (A) The ECG one month before death was normal. (B) The ECG two days prior to death. At that time, the QRS was still normal and only tachycardia and minor repolarization alterations could be seen. Figure 22.5 Serial weights and corresponding sum of the amplitudes of QRS complexes (SQRS) revealing the reciprocal relation of these two variables in this patient (Pt) (Reproduced from Madias et al. 2001, with permission from Elsevier). Figure 22.6 ECGs of two patients, one with non‐ischemic cardiomyopathy (NIC) and the other with ischemic cardiomyopathy (IC). Both ECGs have a similar QRS width, left ventricular ejection fraction (LVEF) and left ventricular end diastolic diameter (LVEDD). Note the pronounced voltages of right precordial leads, particularly in V2 and V3 (arrow), observable in non‐ischemic cardiomyopathy compared to ischemic cardiomyopathy. Although some contradictory results exist, most studies (Vazquez et al. 2009) show that sudden death is more frequently observed in cases of heart failure with reduced ejection fraction, especially in patients with ischemic cardiomyopathy, than in cases of heart failure with preserved ejection fraction. In contrast, there is considerable evidence indicating that several risk markers reflecting ANS alterations (heart rate variability [HRV], heart rate turbulence [HRT], sinus tachycardia) (Cygankiewicz et al. 2006, 2008) may play a role in the risk stratification of sudden death in heart failure patients, although the PPV is low. At the same time, it has been demonstrated that one of the most extensively studied risk markers (T wave alternans) predicts sudden death (Bloomfield et al. 2004; Verrier et al. 2011). However, there is not enough evidence to use these risk markers to guide treatment. The increase of sympathetic innervation, detected by Im‐IBG images, correlates with an improvement in heart failure prognosis and a decrease in ventricular arrhythmias. The MUSIC risk score for predicting death in heart failure (study) (Vazquez et al. 2009) includes 10 independent prognostic variables (Figure 22.7A). It should be emphasized that only atrial enlargement and NT‐pro BNP levels were found to predict death, regardless of the mechanism involved (cardiac death, sudden death, or death due to heart failure progression). A combination of 10 of these variables allowed us to establish a risk score. Figure 22.7B shows the mortality curve according to the type of death studied. With this risk score, two different well‐defined populations were found: one population group with a score < 20, considered a low‐risk population, and a second population group with a score > 20, considered a population with increasing high‐risk. ST2 (Pascual‐Figal et al. 2009) Figure 22.7 (A) Risk score for predicting different types of death. We see the parameters used to determine the score. (B) Mortality curves for the different types of death over a period of three years (Reproduced with permission from Vazquez et al. 2009). It is reasonable to assume that the use of an implantable defibrillator (ICD) (Mirowski et al. 1980) is particularly advisable when in spite of best drug treatment the ejection fraction is below 30%, in patients assessed as Class II or III according to NYHA criteria, or in those with ischemic heart disease (sudden death is more frequent in coronary heart disease than in idiopathic heart disease). Cases with heart failure and a wide QRS complex (> 140 ms) and low ejection fraction (< 30–35%) may be good candidates for resynchronization therapy (biventricular pacemaker) plus ICD (ICD‐CRT therapy) (Cazeau et al. 1994; Moss et al. 1996; Moss 2002; Moss et al. 2009). However, in some cases the only solution might be a heart transplant. Both recipient and donor P waves, the latter always being associated with the QRS complex, may be seen on the surface ECG. Sometimes, it is necessary to utilize a right atrial lead to view the recipient P wave (Figure 22.8). Usually, the donor P wave rate is higher than that of the recipient P wave, since the donor P wave is not under vagal control.
Chapter 22
The ECG in Other Heart Diseases
Valvular heart diseases
Mitral valve disease: ECG changes
Aortic valve disease: ECG changes
Myocarditis and cardiomyopathies
Myocarditis
Concept and evolution
ECG changes during the evolution and differential diagnosis
Restrictive cardiomyopathy
Dilated cardiomyopathy and heart failure
Concept, etiology, and clinical syndromes
ECG changes and prognostic implications
The transplanted heart ECG
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