**27. S-ICD**

An subcutaneous‐ICD (S‐ICD) system contains a subcutaneously implanted lead (in an L‐ configuration) connected to a device inserted subcutaneously, or preferably intramuscular. It effectively terminates ventricular arrhythmias and can offer supportive post‐chock pacing. Current devices cannot be used in patients who need permanent pacing, but technical solutions are developed to combine a leadless pacemaker system communicating with an S‐ICD system. This is beneficial in patients with abnormal vascular anatomy, i.e., malformations or vessel occlusions. But, in young patient, there is an increasing interest in S‐ICD to save vessels for future interventions and avoid short‐term and long‐term vessel‐related complications. S‐ICD has been used in HCM, but careful pre‐operative assessment of possibly risk of T‐wave oversense is of importance in this group. The cost of S‐ICD device is currently much larger than for transvenous device, but this probably diminishes. Studies so far have shown a promising short‐term use of S‐ICD among HCM patients [59].

### **28. Future perspectives**

There remain many challenges in the field of HCM. A detailed understanding of pathophysiologic mechanism of disease progression, arrhythmia substrate and triggers and molecular‐genetic base of the heterogeneous disease is crucial. This could lead to improvement in the therapeutic arsenal, but this development relies on scientific progress in the field of cardiology and basic sciences. Multicentre, prospective registries and other international collaborations to evaluate outcome and refine risk stratification are promising [60, 61].

## **Author details**

#### Peter Magnusson

Address all correspondence to: peter.magnusson@regiongavleborg.se

1 Cardiology Research Unit, Department of Medicine, Karolinska Institute, Karolinska University Hospital, Solna, Stockholm, Sweden

2 Centre for Research and Development, Uppsala University/Region Gävleborg, Gävle, Swe‐ den

### **References**

are associated with poorer mental health. To further address quality of life issues, qualitative

An subcutaneous‐ICD (S‐ICD) system contains a subcutaneously implanted lead (in an L‐ configuration) connected to a device inserted subcutaneously, or preferably intramuscular. It effectively terminates ventricular arrhythmias and can offer supportive post‐chock pacing. Current devices cannot be used in patients who need permanent pacing, but technical solutions are developed to combine a leadless pacemaker system communicating with an S‐ICD system. This is beneficial in patients with abnormal vascular anatomy, i.e., malformations or vessel occlusions. But, in young patient, there is an increasing interest in S‐ICD to save vessels for future interventions and avoid short‐term and long‐term vessel‐related complications. S‐ICD has been used in HCM, but careful pre‐operative assessment of possibly risk of T‐wave oversense is of importance in this group. The cost of S‐ICD device is currently much larger than for transvenous device, but this probably diminishes. Studies so far have shown a

There remain many challenges in the field of HCM. A detailed understanding of pathophysiologic mechanism of disease progression, arrhythmia substrate and triggers and molecular‐genetic base of the heterogeneous disease is crucial. This could lead to improvement in the therapeutic arsenal, but this development relies on scientific progress in the field of cardiology and basic sciences. Multicentre, prospective registries and other international collaborations to evaluate outcome and refine risk stratification are promising [60, 61].

studies may provide valuable insights.

376 Cardiomyopathies - Types and Treatments

**28. Future perspectives**

**Author details**

Peter Magnusson

den

promising short‐term use of S‐ICD among HCM patients [59].

Address all correspondence to: peter.magnusson@regiongavleborg.se

University Hospital, Solna, Stockholm, Sweden

1 Cardiology Research Unit, Department of Medicine, Karolinska Institute, Karolinska

2 Centre for Research and Development, Uppsala University/Region Gävleborg, Gävle, Swe‐

**27. S-ICD**


[22] Maron BJ, Haas TS, Doerer JJ, Thompson PD, Hodges JS. Comparison of U.S. and Italian experiences with sudden cardiac deaths in young competitive athletes and implications for preparticipation screening strategies. Am J Cardiol. 2009;104(2):276‐80. DOI: 10.1016/j.amjcard.2009.03.037

[10] Guttmann OP, Rahman MS, O'Mahony C, Anastasakis A, Elliott PM. Atrial fibrillation and thromboembolism in patients with hypertrophic cardiomyopathy: systematic

[11] Guttmann OP, Pavlou M, O'Mahony C, Monserrat L, Anastasakis A, Rapezzi C, Biagini E, Gimeno JR, Limongelli G, Garcia‐Pavia P, McKenna WJ, Omar RZ, Elliott PM, Hypertrophic Cardiomyopathy Outcomes Investigators. Prediction of thrombo‐ embolic risk in patients with hypertrophic cardiomyopathy (HCM Risk‐CVA). Eur J

[12] Lopes LR, Rahman MS, Elliott PM. A systematic review and meta‐analysis of genotype‐ phenotype associations in patients with hypertrophic cardiomyopathy caused by sarcomeric protein mutations. Heart. 2013;99(24):1800‐11. DOI: 10.1136/heartjnl‐

[13] Morita H, Nagai R, Seidman JG, et al. The impact of genetic testing on hypertrophic cardiomyopathy and heart failure. J Cardiovasc Transl Res. 2010;3:297‐303.

[14] Bos JM, Towbin JA, Ackerman MJ, et al. Diagnostic, prognostic, and therapeutic implications of genetic testing for hypertrophic cardiomyopathy. J Am Coll Cardiol.

[15] Sébillon P, Bouchier C, Bidot LD, Bonne G, Ahamed K, Charron P, Drouin‐ Garraud V, Millaire A, Desrumeaux G, Benaïche A, Charniot JC, Schwartz K, Villard E, Komajda M. Expanding the phenotype of LMNA mutations in dilated cardiomyopathy and functional consequences of these mutations. J Med Genet.

[16] Teare D. Asymmetrical hypertrophy of the heart in young adults. Br Heart J.

[17] Maron BJ, Gardin JM, Flack JM, Gidding SS, Kurosaki TT, Bild DE. Prevalence of hypertrophic cardiomyopathy in a general population of young adults. Echocardio‐ graphic analysis of 4111 subjects in the CARDIA study. Coronary artery risk develop‐

[18] Corrado D, Basso C, Schiavon M, Thiene G. Screening for hypertrophic cardiomyop‐

[19] Semsarian C, Ingles J, Maron MS, Maron BJ. New perspectives on the prevalence of hypertrophic cardiomyopathy. J Am Coll Cardiol. 2015;65(12):1249‐54. DOI: 10.1016/

[20] Caselli S, Maron MS, Urbano‐Moral JA, Pandian NG, Maron BJ, Pelliccia A. Differen‐ tiating left ventricular hypertrophy in athletes from that in patients with hypertrophic cardiomyopathy. Am J Cardiol. 2014;114(9):1383‐9. DOI: 10.1016/j.amjcard.2014.07.070

[21] Ostman‐Smith I. Sudden cardiac death in young athletes. Open Access J Sports Med.

review. Heart. 2014;100(6):465‐72. DOI: 10.1136/heartjnl‐2013‐304276

Heart Fail. 2015;17(8):837‐45. DOI: 10.1002/ejhf.316.

ment in (Young) adults. Circulation. 1995;92(4):785‐9.

athy in young athletes. N Engl J Med. 1998;339(6):364‐9.

2011;2:85‐97. DOI: 10.2147/OAJSM.S10675.

2013‐303939.

378 Cardiomyopathies - Types and Treatments

2009;54:201‐11.

2003;40(8):560‐7.

j.jacc.2015.01.019.

1958;20:1‐18.


Rodríguez García J, Tascón Pérez JC. Sequential atrioventricular pacing in patients with hypertrophic cardiomyopathy: an 18‐year experience. Rev Esp Cardiol (Engl Ed). 2016;69(4):377‐83. DOI: 10.1016/j.rec.2015.08.023.


Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2011;58:e212‐60.

[41] Christiaans I, van Engelen K, van Langen IM, et al. Risk stratification for sudden cardiac death in hypertrophic cardiomyopathy: systematic review of clinical risk markers. Europace. 2010;12:313‐21.

Rodríguez García J, Tascón Pérez JC. Sequential atrioventricular pacing in patients with hypertrophic cardiomyopathy: an 18‐year experience. Rev Esp Cardiol (Engl Ed).

[33] Rogers DP, Marazia S, Chow AW, Lambiase PD, Lowe MD, Frenneaux M, et al. Effect of biventricular pacing on symptoms and cardiac remodelling in patients with end‐

[34] Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JG, Coats AJ, Falk V, González‐ Juanatey JR, Harjola VP, Jankowska EA, Jessup M, Linde C, Nihoyannopoulos P, Parissis JT, Pieske B, Riley JP, Rosano GM, Ruilope LM, Ruschitzka F, Rutten FH, van der Meer P; Authors/Task Force Members; Document Reviewers. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure: the Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC). Developed with the special contribution of the Heart Failure Association (HFA) of the ESC. Eur J Heart Fail. 2016;18(8):891‐975. DOI: 10.1002/ejhf.

[35] Magnusson P, Gadler F, Liv P, Mörner S. Risk markers and appropriate implantable defibrillator therapy in hypertrophic cardiomyopathy. Pacing Clin Electrophysiol.

[36] Kato TS, Takayama H, Yoshizawa S, Marboe C, Schulze PC, Farr M, Naka Y, Mancini D, Maurer MS. Cardiac transplantation in patients with hypertrophic cardiomyopathy. Am J Cardiol. 2012;110(4):568‐74. DOI: 10.1016/j.amjcard.2012.04.030. Epub 15 May

[37] Wynne E, Bergin JD, Ailawadi G, Kern JA, Kennedy JL. Use of a left ventricular assist device in hypertrophic cardiomyopathy. J Card Surg. 2011;26(6):663‐5. DOI: 10.1111/j.

[38] Maron BJ, Spirito P, Shen WK, Haas TS, Formisano F, Link MS, Epstein AE, Almquist AK, Daubert JP, Lawrenz T, Boriani G, Estes NA 3rd, Favale S, Piccininno M, Winters SL, Santini M, Betocchi S, Arribas F, Sherrid MV, Buja G, Semsarian C, Bruzzi P. Implantable cardioverter‐defibrillators and prevention of sudden cardiac death in

[39] Maron BJ, McKenna WJ, Danielson GK, et al. American College of Cardiology/ European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy. A report of the American College of Cardiology Foundation Task Force on clinical expert consensus documents and the European Society of Cardiology

[40] Gersh BJ, Maron BJ, Bonow RO, et al. 2011 ACCF/AHA Guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines developed in collaboration with the American Association for Thoracic Surgery, American Society of Echocardiography, American

Committee for practice guidelines. J Am Coll Cardiol. 2003;42:1687‐713.

hypertrophic cardiomyopathy. JAMA. 2007;298(4):405‐12

stage hypertrophic cardiomyopathy. Eur J Heart Fail. 2008;10:507‐13.

2016;69(4):377‐83. DOI: 10.1016/j.rec.2015.08.023.

2016;39(3):291‐301. DOI: 10.1111/pace.12801

592.

380 Cardiomyopathies - Types and Treatments

2012.

1540‐8191.2011.01331.x.


international, observational study of hypertrophic cardiomyopathy. Am Heart J. 2015;170(2):223‐30. DOI: 10.1016/j.ahj.2015.05.013.

[61] Elliott P, Charron P, Blanes JR, Tavazzi L, Tendera M, Konté M, Laroche C, Maggioni AP; EORP Cardiomyopathy Registry Pilot Investigators. European cardiomyopathy pilot registry: EURObservational Research Programme of the European Society of Cardiology. Eur Heart J. 2016;37(2):164‐73. DOI: 10.1093/eurheartj/ehv497

[50] Coats CJ, Rantell K, Bartnik A, Patel A, Mist B, McKenna WJ, Elliott PM. Cardiopul‐ monary exercise testing and prognosis in hypertrophic cardiomyopathy. Circ Heart

[51] Elliott PM, Gimeno JR, Tomé MT, Shah J, Ward D, Thaman R, et al. Left ventricular outflow tract obstruction and sudden death risk in patients with hypertrophic cardio‐

[52] Autore C, Bernabò P, Barillà CS, et al. The prognostic importance of left ventricular outflow obstruction in hypertrophic cardiomyopathy varies in relation to the severity

[53] Ismail TF, Jabbour A, Gulati A, Mallorie A, Raza S, Cowling TE, Das B, Khwaja J, Alpendurada FD, Wage R, Roughton M, McKenna WJ, Moon JC, Varnava A, Shake‐ speare C, Cowie MR, Cook SA, Elliott P, O'Hanlon R, Pennell DJ, Prasad SK. Role of late gadolinium enhancement cardiovascular magnetic resonance in the risk stratifica‐ tion of hypertrophic cardiomyopathy. Heart. 2014;100(23):1851‐8. DOI: 10.1136/

[54] Maron BJ, Shen WK, Link MS, Epstein AE, Almquist AK, Daubert JP, Bardy GH, Favale S, Rea RF, Boriani G, Estes NA 3rd, Spirito P. Efficacy of implantable cardioverter‐ defibrillators for the prevention of sudden death in patients with hypertrophic

[55] Magnusson P, Gadler F, Liv P, Mörner S. Hypertrophic cardiomyopathy and implant‐ able defibrillators in Sweden: inappropriate shocks and complications requiring surgery. J Cardiovasc Electrophysiol. 2015;26(10):1088‐94. DOI: 10.1111/jce.12750. [56] Magnusson P, Gadler F, Liv P, Mörner S. Causes of death and mortality in hypertrophic cardiomyopathy patients with implantable defibrillators in Sweden. J Cardiovasc Med

[57] Cox S, O'Donoghue AC, McKenna WJ, Steptoe A. Health related quality of life and psychological wellbeing in patients with hypertrophic cardiomyopathy. Heart.

[58] Magnusson P, Mörner S, Gadler F, Karlsson J. Health‐related quality of life in hyper‐ trophic cardiomyopathy patients with implantable defibrillators. Health Qual Life

[59] Weinstock J, Bader YH, Maron MS, Rowin EJ, Link MS. Subcutaneous implantable cardioverter defibrillator in patients with hypertrophic cardiomyopathy: an initial experience. J Am Heart Assoc. 2016 Feb 12;5(2). pii: e002488. doi: 10.1161/JAHA.

[60] Kramer CM, Appelbaum E, Desai MY, Desvigne‐Nickens P, DiMarco JP, Friedrich MG, Geller N, Heckler S, Ho CY, Jerosch‐Herold M, Ivey EA, Keleti J, Kim DY, Kolm P, Kwong RY, Maron MS, Schulz‐Menger J, Piechnik S, Watkins H, Weintraub WS, Wu P, Neubauer S.Hypertrophic cardiomyopathy registry: the rationale and design of an

(Hagerstown). 2016;17(7):478‐84. DOI: 10.2459/JCM.0000000000000359.

Fail. 2015;8(6):1022‐31. DOI: 10.1161/CIRCHEARTFAILURE.

myopathy. Eur Heart J. 2006;27:1933‐41.

heartjnl‐2013‐305471.

382 Cardiomyopathies - Types and Treatments

1997;78(2):182‐7.

115.002488.

of symptoms. J Am Coll Cardiol. 2005;45:1078‐80.

cardiomyopathy. N Engl J Med. 2000;342(6):365‐73.

Outcomes. 2016;14:62. DOI: 10.1186/s12955‐016‐0467‐x.

#### **Electrical Devices (Resynchronization and Defibrillators) in the Treatment of Cardiomyopathies: Indications, Present and Future of these Therapies** Electrical Devices (Resynchronization and Defibrillators) in the Treatment of Cardiomyopathies: Indications, Present and Future of these Therapies

Miguel Ángel García García, María de los Ángeles Rosero Arenas, Alfonso Martínez Cornejo, Marta Bertolo Domínguez and Vicente Miranda Gozalvo Miguel Ángel García García, María de los Ángeles Rosero Arenas, Alfonso Martínez Cornejo, Marta Bertolo Domínguez and Vicente Miranda Gozalvo

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/65317

#### Abstract

Cardiomyopathies are heart diseases involving high risk of heart failure and sudden cardiac death. In this chapter, we review the use of electrical devices (cardiac resynchronization therapy and implantable cardioverter defibrillator) to reduce the progression of heart failure and prevent arrhythmogenic sudden death in patients affected with these pathologies. The future of these therapies is a more appropriate indication for primary prevention of sudden death (defibrillator) and treatment of heart failure in a broader spectrum of patients (resynchronization).

Keywords: cardiac resynchronization therapy, implantable cardioverter defibrillator, cardiomyopathy, heart failure, sudden death

### 1. Introduction

Cardiomyopathies (CMP) are a group of diseases that affect the cardiac muscle associated with myocardial dysfunction and can be caused by known disorders such as hypertension, ischemic heart disease, valvular disease, and so on. Other causes, such as genetic illnesses, inflammatory processes, metabolic, or toxic diseases, may also be responsible for this pathology. Its origin could also be primary, i.e., not known cause. One simple and initial classification of the CMP divides them into ischemic and nonischemic ones. In 1995, the World Health Organization (WHO)/International Society and Federation of Cardiology (ISFC) Task Force on the Definition

© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

and Classification of the Cardiomyopathies classified them into dilated, hypertrophic, restrictive, arrhythmogenic right ventricular dysplasia, and other [1]. Since these diseases can have mechanical and/or electrical dysfunction, in this chapter, we review the usefulness of electrical therapies (cardiac resynchronization therapy or/and implantable cardioverter defibrillator) to treat heart failure and arrhythmogenic sudden cardiac death associated with these diseases.

The etiology of heart failure may be predictive of long-term outcome: survival of peripartum CMP was better; medium in hypertension, myocarditis, sarcoidosis, and substance abuse; and worse in infiltrative myocardial disease –amyloidosis and hemochromatosis-, HIV disease, chemotherapy with doxorubicin, ischemic heart disease, or connective tissue disease. And in all of them, the added presence of diabetes involves an increased risk of mortality.

Heart failure is a complex clinical syndrome that causes inadequate systemic perfusion to meet the body's metabolic demands with usually increased left ventricular filling pressures. The two leading causes of death in patients with heart failure are arrhythmic or sudden cardiac death and progressive pump failure [2]. Life-threatening ventricular arrhythmias are common in patients with heart failure and CMP, and unexpected sudden cardiac death and sudden cardiac death during episodes of clinical worsening of heart failure each account for approximately one-third of deaths. Management of patients with heart failure includes several strategies: controlling contributing factors, lifestyle modification, pharmacological therapy, rehabilitation, preventive care, and electrical devices if indicated. The mode of death in patients with heart failure is more likely to be "sudden" in patients with New York Heart Association (NYHA) II-III classes and related to pump failure in patients with NYHA IV class [3].

Ventricular arrhythmias are common in heart failure and CMP. The prognosis of these arrhythmias depends on the cause of the CMP [4]. There is no preventive drug therapy to treat ventricular arrhythmias (i.e., amiodarone). However, those patients with nonsustained ventricular tachycardia may be candidates (with preliminary electrophysiological study) to an implantable cardioverter defibrillator. Patients with spontaneous sustained ventricular tachycardia are at high risk for sudden cardiac death; patients with heart failure or CMP who are survivors of sudden cardiac death due to ventricular tachycardia or ventricular fibrillation must be treated with implantable cardioverter defibrillator for secondary prevention [4, 5] (Figure 1).

A pacemaker placed in right ventricle can exacerbate heart failure by several mechanisms: firstly, contraction of the right ventricle before the left ventricle (interventricular dyssynchrony), and secondly the "left bundle branch block effect" causing that septum contracts before the lateral wall (intraventricular dyssynchrony); the final outcome of both phenomena results in a reduced efficiency of cardiac pump. It is likely that a pacemaker placed in right atrium and right ventricle provides benefit in heart failure, but DAVID trial, which included patients with left ventricular ejection fraction ≤40% and without indication for bradycardia showed that pacing with DDD function (dual, atrial and ventricular, pacing and sensing, and also dual, triggered and inihibited, response to sensing, according to accepted international code accepted in 2002) [6] can worsen heart failure. The same concept could be generalized to patients with CMP [7].

Therapy known as cardiac resynchronization can optimize cardiac function, symptoms, and survival in patients with heart failure with left ventricular dysfunction (with left ventricular

Electrical Devices (Resynchronization and Defibrillators) in the Treatment of Cardiomyopathies... http://dx.doi.org/10.5772/65317 387

Figure 1. Endocavitary registry of two ventricular arrhythmias: ventricular tachycardia, treated with anti-tachycardia pacing (ATP), and ventricular fibrillation, treated with defibrillation (0.4 J).

ejection fraction ≤35% and wide QRS with left bundle branch block), added to optimal medical treatment. On the other hand, implantable cardioverter defibrillator can abort sudden arrhythmic deaths, thus prolonging survival in patients with cardiac disease and that patients may progress in later stages to more advanced heart failure.

### 2. Ischemic CMP

and Classification of the Cardiomyopathies classified them into dilated, hypertrophic, restrictive, arrhythmogenic right ventricular dysplasia, and other [1]. Since these diseases can have mechanical and/or electrical dysfunction, in this chapter, we review the usefulness of electrical therapies (cardiac resynchronization therapy or/and implantable cardioverter defibrillator) to treat heart failure and arrhythmogenic sudden cardiac death associated with these diseases. The etiology of heart failure may be predictive of long-term outcome: survival of peripartum CMP was better; medium in hypertension, myocarditis, sarcoidosis, and substance abuse; and worse in infiltrative myocardial disease –amyloidosis and hemochromatosis-, HIV disease, chemotherapy with doxorubicin, ischemic heart disease, or connective tissue disease. And in

Heart failure is a complex clinical syndrome that causes inadequate systemic perfusion to meet the body's metabolic demands with usually increased left ventricular filling pressures. The two leading causes of death in patients with heart failure are arrhythmic or sudden cardiac death and progressive pump failure [2]. Life-threatening ventricular arrhythmias are common in patients with heart failure and CMP, and unexpected sudden cardiac death and sudden cardiac death during episodes of clinical worsening of heart failure each account for approximately one-third of deaths. Management of patients with heart failure includes several strategies: controlling contributing factors, lifestyle modification, pharmacological therapy, rehabilitation, preventive care, and electrical devices if indicated. The mode of death in patients with heart failure is more likely to be "sudden" in patients with New York Heart Association (NYHA) II-

Ventricular arrhythmias are common in heart failure and CMP. The prognosis of these arrhythmias depends on the cause of the CMP [4]. There is no preventive drug therapy to treat ventricular arrhythmias (i.e., amiodarone). However, those patients with nonsustained ventricular tachycardia may be candidates (with preliminary electrophysiological study) to an implantable cardioverter defibrillator. Patients with spontaneous sustained ventricular tachycardia are at high risk for sudden cardiac death; patients with heart failure or CMP who are survivors of sudden cardiac death due to ventricular tachycardia or ventricular fibrillation must be treated with implantable cardioverter defibrillator for secondary prevention [4, 5]

A pacemaker placed in right ventricle can exacerbate heart failure by several mechanisms: firstly, contraction of the right ventricle before the left ventricle (interventricular dyssynchrony), and secondly the "left bundle branch block effect" causing that septum contracts before the lateral wall (intraventricular dyssynchrony); the final outcome of both phenomena results in a reduced efficiency of cardiac pump. It is likely that a pacemaker placed in right atrium and right ventricle provides benefit in heart failure, but DAVID trial, which included patients with left ventricular ejection fraction ≤40% and without indication for bradycardia showed that pacing with DDD function (dual, atrial and ventricular, pacing and sensing, and also dual, triggered and inihibited, response to sensing, according to accepted international code accepted in 2002) [6] can worsen heart failure. The same concept could be

Therapy known as cardiac resynchronization can optimize cardiac function, symptoms, and survival in patients with heart failure with left ventricular dysfunction (with left ventricular

all of them, the added presence of diabetes involves an increased risk of mortality.

III classes and related to pump failure in patients with NYHA IV class [3].

(Figure 1).

386 Cardiomyopathies - Types and Treatments

generalized to patients with CMP [7].

Risk stratification of a patient who has an acute myocardial infarction and ischemic CMP should include: identification of risk for recurrent ischemic events and identification of high risk of death (arrhythmic or non-arrhythmic of origin). Postinfarction mortality has decreased by optimizing the initial therapy (reperfusion) and secondary prevention measures [4].

### 2.1. Role of implantable cardioverter defibrillator

Several works (VALIANT [8]) described an increased risk of sudden cardiac death in patients with postinfarction left ventricular failure; the rate of sudden cardiac death or resuscitated cardiac arrest was 1.4 % in the first month, with a rate of 2.3% if left ventricular ejection fraction <30%), but the frequency of use of reperfusion therapy and beta-blockers was low. Two studies (DINAMIT [9] and IRIS [10]) showed no improvement in survival after implantable cardioverter defibrillator placement between 31 and 40 days post infarction. Several risk factors are associated with threatening arrhythmia: low ejection fraction of left ventricle or history of heart failure, ventricular tachycardia induced in the electrophysiologic study, spontaneous ventricular premature beats and nonsustained ventricular tachycardia seen in the 24-hour Holter, and other. On the other hand, reperfusion therapy has decreased the predictive value of these variables. Finally, implantable cardioverter defibrillator should be recommended in patients with a left ventricular ejection fraction ≤30% (MADIT II criteria) or with ischemic CMP, left ventricular ejection fraction ≤35%, and NYHA II or III heart failure (SCD-HEFT criteria) [11] (Figure 2). In recent guidelines [12, 13], implantable cardioverter defibrillator is an effective therapy to reduce sudden cardiac death in patients with previous myocardial infarction and left ventricular dysfunction, which have hemodynamically unstable sustained ventricular tachycardia, and in patients with recurrent ventricular tachycardia and normal/near normal left ventricular function.

#### 2.2. Role of cardiac resynchronization therapy

The usefulness of resynchronization is demonstrated in patients with ischemic CMP. In several pivotal studies, which demonstrated the utility of resynchronization (CARE-HF, COMPAN-ION, etc), there was a significant percentage of patients with ischemic CMP. In other old studies [14], patients with ischemic CMP may respond less favorably to resynchronization compared with patients with idiopathic dilated CMP. In recent years, studies comparing the effectiveness of this therapy in ischemic vs dilated CMP have been developed [15]; estimated survival at 4 years were 55% for ischemic and 77% for dilated CMP, and no significant difference was found in the incidence of inappropriate implantable cardioverter defibrillator shocks between both groups. Patients with implantable cardioverter defibrillator functionality remained at higher risk for death after controlling for pre-implant variables (hazard ratio (HR), 1.6). So, patients with dilated CMP experienced greater improvement in left ventricular systolic function and reverse remodeling than those with ischemic CMP, which means sustaining a greater survival benefit.

Another study [16] showed that after atrioventricular node ablation along with biventricular pacemaker placement, in patients with heart failure and refractory atrial fibrillation, echocardiographic reverse remodeling was lower in patients with ischemic compared with dilated CMP [16], with a greater number of hospitalizations due to heart failure in this first group and less improvement of left ventricular ejection fraction.

Finally, a combination of resynchronization + surgery in dilated ischemic CMP could be useful: optimization of ventricular function by myocardial revascularization with synchronized contraction of papillary muscle by biventricular pacing could improve the abnormal conformation/shape of the left ventricle, responsible for the functional mitral regurgitation. Therefore, preoperative assessment of myocardial viability and synchronism of the papillary muscles is the key to the success of this intervention.

Recent clinical guidelines [17] show greater benefit of CRT in several subgroups: women, QRS ≥150 ms, and nonischemic CMP. Despite the lower efficacy against nonischemic patients, the implant in these patients is recommended.

Electrical Devices (Resynchronization and Defibrillators) in the Treatment of Cardiomyopathies... http://dx.doi.org/10.5772/65317 389

Figure 2. Monocameral implantable cardioverter defibrillator in a patient with ischemic dilated cardiomyopathy.

### 3. Myocarditis

(DINAMIT [9] and IRIS [10]) showed no improvement in survival after implantable cardioverter defibrillator placement between 31 and 40 days post infarction. Several risk factors are associated with threatening arrhythmia: low ejection fraction of left ventricle or history of heart failure, ventricular tachycardia induced in the electrophysiologic study, spontaneous ventricular premature beats and nonsustained ventricular tachycardia seen in the 24-hour Holter, and other. On the other hand, reperfusion therapy has decreased the predictive value of these variables. Finally, implantable cardioverter defibrillator should be recommended in patients with a left ventricular ejection fraction ≤30% (MADIT II criteria) or with ischemic CMP, left ventricular ejection fraction ≤35%, and NYHA II or III heart failure (SCD-HEFT criteria) [11] (Figure 2). In recent guidelines [12, 13], implantable cardioverter defibrillator is an effective therapy to reduce sudden cardiac death in patients with previous myocardial infarction and left ventricular dysfunction, which have hemodynamically unstable sustained ventricular tachycardia, and in patients with recur-

The usefulness of resynchronization is demonstrated in patients with ischemic CMP. In several pivotal studies, which demonstrated the utility of resynchronization (CARE-HF, COMPAN-ION, etc), there was a significant percentage of patients with ischemic CMP. In other old studies [14], patients with ischemic CMP may respond less favorably to resynchronization compared with patients with idiopathic dilated CMP. In recent years, studies comparing the effectiveness of this therapy in ischemic vs dilated CMP have been developed [15]; estimated survival at 4 years were 55% for ischemic and 77% for dilated CMP, and no significant difference was found in the incidence of inappropriate implantable cardioverter defibrillator shocks between both groups. Patients with implantable cardioverter defibrillator functionality remained at higher risk for death after controlling for pre-implant variables (hazard ratio (HR), 1.6). So, patients with dilated CMP experienced greater improvement in left ventricular systolic function and reverse remodeling than those with ischemic CMP, which means sustaining a

Another study [16] showed that after atrioventricular node ablation along with biventricular pacemaker placement, in patients with heart failure and refractory atrial fibrillation, echocardiographic reverse remodeling was lower in patients with ischemic compared with dilated CMP [16], with a greater number of hospitalizations due to heart failure in this first group and

Finally, a combination of resynchronization + surgery in dilated ischemic CMP could be useful: optimization of ventricular function by myocardial revascularization with synchronized contraction of papillary muscle by biventricular pacing could improve the abnormal conformation/shape of the left ventricle, responsible for the functional mitral regurgitation. Therefore, preoperative assessment of myocardial viability and synchronism of the papillary muscles is

Recent clinical guidelines [17] show greater benefit of CRT in several subgroups: women, QRS ≥150 ms, and nonischemic CMP. Despite the lower efficacy against nonischemic patients, the

rent ventricular tachycardia and normal/near normal left ventricular function.

2.2. Role of cardiac resynchronization therapy

388 Cardiomyopathies - Types and Treatments

less improvement of left ventricular ejection fraction.

the key to the success of this intervention.

implant in these patients is recommended.

greater survival benefit.

It is an inflammatory disease of the myocardium, characterized from a histopathologic point of view by inflammatory infiltrates within the myocardium associated with degeneration and necrosis, with a nonischemic origin. The most common etiology is infectious, followed by immune (drugs, autoimmune diseases, etc) and toxic (drugs, metals, radiation, etc). Acute myocarditis can lead to chronic myocarditis or dilated CMP up to 10% of cases [18, 19]. In patients with sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation, and/or dilated CMP with ventricular dysfunction, the decision to implant and implantable cardioverter defibrillator should be based on the same indications as in other CMP, according to clinical practice guidelines [13]. It seems reasonable to delay the placement of an implantable cardioverter defibrillator until the resolution of the acute episode, meanwhile can be raised using a vest defibrillator as a bridge in high-risk patients [20]. Once dilated CMP has been developed, implantation of a cardiac resynchronization therapy device is recommended in patients with severe depression of left ventricular systolic function (<35%) and left bundle block in functional class II–IV [21].

In clinical guidelines [12, 13], implantable cardioverter defibrillator is indicated if inflammatory infiltrates persist in biopsies and if there is abnormal fibrosis in magnetic resonance; these elements are risk factors for sudden cardiac death.
