Keywords

6.1 Spectrum of Disease

Before diagnosing dilated cardiomyopathy (DCM), it is necessary to exclude conditions with phenotypic overlap. A comprehensive integrated approach to patients with a newly diagnosed DCM is essential in order to achieve an accurate early prognostic stratification.

In many DCM individuals, there is a preclinical phase without cardiac expression that subsequently progresses toward mild cardiac abnormalities, such as isolated left ventricular (LV) dilatation, subtle systolic dysfunction, or arrhythmogenic features (ventricular or supraventricular arrhythmia or conduction defects) that can be observed in myocarditis [1, 2] or in the early phase of genetic diseases [3]. The overt phase of systolic dysfunction is usually associated with LV dilatation, but this may be absent in some cases causing diagnostic confusion (described in Lamin A/C gene mutation carriers [4, 5] and also in some patients without a known genetic cause [6,7,8] (Fig. 6.1).

Fig. 6.1
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Dilated cardiomyopathy: spectrum of disease

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Thus, in this context every effort has to be made to obtain an accurate diagnosis (cardiac magnetic resonance (CMR), endomyocardial biopsy (EMB), biomarkers, etc.), with the aim to personalize patient management according to specific etiology.

The prognosis of DCM has improved in the course of the past years [9] with the use of evidence-based therapies, both pharmacological and non-pharmacological [10,11,12], and also due to the constant effort to diagnose this cardiomyopathy in the early stages (Figs. 6.2, 6.3, and 6.4) [13]. Identifying patients with DCM in an asymptomatic phase is equivalent to early diagnosis and guarantees a better long-term survival for the patients [14].

Fig. 6.2
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Cause specific KM: survival free from all-cause mortality/heart transplant in IDCM patients according to the decade of enrolment. From Merlo et al., Long-term prognostic impact of therapeutic strategies in patients with idiopathic dilated cardiomyopathy: changing mortality over the last 30 years, Eur J Heart Fail, 2014; 16(3):317–24

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Fig. 6.3
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Cause-specific KM curves: survival free from pump failure death/heart transplant in IDCM patients according to the decade of enrolment. From Merlo et al., Long-term prognostic impact of therapeutic strategies in patients with idiopathic dilated cardiomyopathy: changing mortality over the last 30 years, Eur J Heart Fail, 2014; 16(3):317–24

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Fig. 6.4
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Cause-specific KM curves: survival free from sudden death in IDCM patients according to the decade of enrolment. From Merlo et al., Long-term prognostic impact of therapeutic strategies in patients with idiopathic dilated cardiomyopathy: changing mortality over the last 30 years, Eur J Heart Fail, 2014; 16(3):317–24

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6.2 Clinical Presentation

In old series, initial symptoms of heart failure were present in 80% of patients with DCM [15]. These symptoms include excessive sweating, orthopnea, and fatigue after mild exertion. Abdominal discomfort, nausea, anorexia, and cachexia can be prominent in advanced cases. Circulatory collapse is the most severe manifestation of congestive heart failure. Thromboembolic events and, rarely, sudden cardiac death (SCD) might be the initial symptom, particularly in infants. Other symptoms include those related to ventricular or supraventricular arrhythmias (i.e., palpitations, syncope, fatigue).

In more recent years, however, the clinical presentation has somehow changed. In fact, the diagnosis often now occurs in asymptomatic individuals, mostly due to family and sports screening programs. Careful attention has to be made in evaluating the arrhythmic risk of these patients, since a non-negligible number of events can occur in the first months following the diagnosis.

Despite recent advances in medical treatment, LV dysfunction associated with signs of congestive heart failure (HF) is characterized by significant mortality [16]. Patients may progress through an asymptomatic phase of LV systolic dysfunction of various degrees, from mild to severe, before the development of overt HF [17,18,19]. LV dysfunction has frequently a progressive nature, and that is the reason for increasing interest regarding its preclinical state.

Most patients affected by DCM who present clinically with HF show symptoms and signs due to excess fluid accumulation (dyspnea, orthopnea, edema, pain from hepatic congestion, and abdominal discomfort due to ascites), sometimes associated with those due to a reduction in cardiac output (fatigue, weakness) [20].

In most patients with HF who require hospitalization, the reason for admission is volume overload. In clinical practice, four signs are commonly used to predict elevated filling pressures: jugular venous distention/abdominojugular reflux, presence of an S3 and/or S4, rales, and pedal edema. According to current international guidelines on HF [21, 22], the patient with HF can be clinically assessed along two basic axes—volume status (“dry” or “wet”) and perfusion status (“warm” or “cold”)—as a useful guide to therapy.

This approach has prognostic usefulness, particularly in assessing patients at discharge after admission for heart failure. For example, such patients discharged with a “wet” or “cold” profile experience worse outcomes (HR, 1.5; 95% CI, 1.1–12.1; P = 0.017) compared with those discharged “warm and dry” (HR 0.9; 95% CI, 0.7–2.1; P = 0.5) [23].

In chronic presentations (months), symptoms as peripheral edema, abdominal distension, and anorexia may be more pronounced than dyspnea.

On the other hand, a decompensated chronic HF can lead to low-output symptoms.

Four major findings suggest severity of the cardiac dysfunction and low output: resting sinus tachycardia, narrow pulse pressure, diaphoresis, and peripheral vasoconstriction.

An irregularly irregular pulse is suggestive of atrial fibrillation which frequently accompanies HF. Pulsus alternans is a sign of severe left ventricular (LV) systolic failure. This phenomenon is characterized by evenly spaced alternating strong and weak peripheral pulses.

A laterally displaced apical impulse that is past the midclavicular line is usually indicative of LV enlargement.

An S3 gallop is associated with left atrial pressures exceeding 20 mmHg and increased LV end-diastolic pressures (>15 mmHg).

An apical systolic murmur is associated with mitral regurgitation, often present in these patients.

Patients with chronic HF often develop secondary pulmonary hypertension, which can contribute to dyspnea as pulmonary pressures rise with exertion. These patients may also complain of substernal chest pressure, typical of angina. In this setting, elevated right ventricular end-diastolic pressure leads to secondary right ventricular subendocardial ischemia. Physical signs of pulmonary hypertension can include increased intensity of P2, a murmur of pulmonary insufficiency, a parasternal lift, and a palpable pulmonic tap (felt in the left second intercostal space) [20].

In patients with arrhythmic presentation, the onset of the disease may be the presence of palpitations, syncopal or near-syncopal episodes, or in some of them SCD. Thus, arrhythmic risk stratification is a major concern, as discussed in the following chapters.

6.3 Natural History

In the past, the prognosis of DCM was considered ominous [24], and the disease was frequently progressive to death due to HF or heart transplantation.

By time the patients are diagnosed, they often have severe contractile dysfunction and remodeling of the ventricles, reflecting a long period of asymptomatic silent disease progression.

However, implementation of optimal pharmacological and non-pharmacological treatments has dramatically improved the prognosis of DCM [25] with an estimated survival free from death or heart transplantation up to 85% at 10 years [13, 26, 27] (Table 6.1).

Table 6.1 Occurrence of major events in patients with DCM according to the decade of enrolment
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Moreover, the lower prevalence of comorbidities when compared to most patients with other forms of systolic LV dysfunction suggests that individuals with DCM tend to have fewer non-cardiovascular events [25]. In hypertensive heart disease, for example, there is a lower incidence of arrhythmic events and a greater competitive risk of non-cardiovascular events [28].

The improved outcomes in DCM are paralleled by a higher rate of LV reverse remodeling (LVRR): in recent years several studies revealed that almost 40% of patients experience a significant LVRR when treated with evidence-based pharmacological and device treatments [26].

From a pure mechanistic standpoint, LVRR is the result of either the removal of the noxious stimuli that triggered cardiac dysfunction or of the institution of therapies favorably interfering with the process of LV remodeling. Factors recognized to trigger or amplify LV remodeling include changes in myocardial wall tension and neurohormonal activation. Initially a compensatory process, the release of hypovolemic hormones (such as renin, antidiuretic hormone, and norepinephrine) eventually contributes to the progression of DCM, and pharmacologic therapies that reduce neurohormonal activation have been shown to promote LVRR [29].

The process of LVRR may take up to 2 years following diagnosis. The following aspects, evaluated at baseline and during follow-up, have been demonstrated as influencing the course and the prognosis of the disease and the likelihood of LVRR in the early stages and should be hence systematically assessed:

  1. (a)

    Right ventricular function at diagnosis is an important prognostic feature in DCM [30]. The recovery of right ventricular function under therapy is frequent and can already be observed at 6 months. It precedes LVRR and is emerging as an early therapeutic target and an independent prognostic predictor [31]. Improvement in right ventricular function is also described in CRT recipients as a secondary expression of hemodynamic improvement very early after resynchronization, with consequently favorable survival rates [32]. In contrast, the development of right ventricular dysfunction during long-term follow-up is an expression of structural progression of the disease and portends a negative outcome [31].

  2. (b)

    Functional mitral regurgitation conveys important prognostic implications. Moderate to severe mitral regurgitation at diagnosis or persistent despite optimal medical treatment or CRT is associated with poorer outcomes [32, 33]. Patients with DCM and hemodynamically important mitral regurgitation may require invasive therapeutic strategies such as percutaneous repair of the mitral valve, mechanical circulatory support, or even heart transplantation.

  3. (c)

    Left bundle branch block (LBBB) is a frequent ECG marker at diagnosis and is negatively associated with the likelihood of LVRR [26]. Importantly the development of new LBBB during follow-up is a strong independent prognostic predictor of all-cause mortality [34].

  4. (d)

    The onset of atrial fibrillation during the follow-up is a sign of structural progression of the disease and negatively impacts on the prognosis of these patients, despite effective treatments [35].

  5. (e)

    In patients with DCM, the persistence of restrictive filing at 3 months after presentation is associated with a high mortality and transplantation rate. On the other hand, patients with reversible restrictive filling have a high probability of improvement and excellent survival. Thus, reassessment of these patients after 3 months of therapy gives additional prognostic information with respect to the initial evaluation [36].

The implications of these observations are that a multi-parametric approach to diagnosis and long-term follow-up, not limited to the LV systolic function and size alone, appear essential in order to improve the quality of clinical management of DCM patients [37].

In spite of this therapeutic success, emerging evidence suggests that some patients remain vulnerable to SCD and refractory HF requiring heart transplant or mechanical circulatory support [26].

Thus, the outcome of patients with DCM often remains unpredictable, and major adverse events may occur in the first months following the diagnosis [7, 38].

Furthermore, even when there is improvement in LV dysfunction, the potential for later decline in systolic function remains, despite uninterrupted treatment [37].

Sometimes LVRR is pronounced enough to result in a normalization of both LVEF and LV diameters, in a process that has been referred to as “apparent healing” or “myocardial remission” [39]. Nevertheless, in a retrospective observational study, only about 10% of DCM patients showed persistent apparent healing at long term (10 years), but the vast majority of them experienced a recurrence of LV dysfunction in a very long term, thus suggesting that the observed healing was only apparent and that true myocardial recovery is at most a rare event in DCM patients [40, 41].

This last issue emphasizes the pivotal role not only of an accurate and complete initial diagnostic evaluation but also of continuous and tailored, modulated therapy and individualized, long-term accurate surveillance in order to recognize and treat the first signs of late disease progression (Fig. 6.5).

Fig. 6.5
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Natural history of dilated cardiomyopathy. Early prognostic stratification and continuous restratification during long-term follow-up are fundamental in order to better identify those at higher risk of sudden cardiac death (arrow)

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Modern management of HF has increased the survival rates of DCM and has resulted in long periods of clinical stability [25, 42]. Consequently, affected patients followed for beyond 10–15 years are often encountered in clinical practice.

It has to be noted, in addition, that the patients should be continuously and critically reassessed, particularly in the presence of cardiovascular risk factors. Indeed, abrupt worsening of LV function or an increased ventricular arrhythmic burden can be caused not only by the DCM progression but also by the development of new co-pathologies. Therefore, the possible presence of coronary artery disease, hypertensive heart disease, structured valve disease, or an acute myocarditis should be systematically ruled out during the follow-up [37].