Cardiovascular considerations in the management of neuromuscular disease

Beneficial effects of beta-blockers and angiotensin-converting enzyme inhibitors in Duchenne muscular dystrophy

BACKGROUND

Patients with Duchenne muscular dystrophy (DMD) often have severe heart failure with a high mortality rate. Most DMD patients with cardiomyopathy became symptomatic in their early to middle teens and usually die of congestive heart failure within 2-3 years from the onset of symptoms. It has been reported that the combination of an angiotensin-converting enzyme (ACE) inhibitor and a beta-blocker has additive benefits in patients with heart failure. The aim of this study was to assess whether the combination of an ACE inhibitor and a beta-blocker is associated with long-term survival of DMD patients with left ventricular (LV) dysfunction.

METHODS

We retrospectively analyzed the outcomes of 52 DMD patients who had begun treatment for heart failure with an ACE inhibitor and a beta-blocker at National Yakumo Hospital during the period from 1992 to 2005. All patients used wheelchairs in their daily lives. Patients were classified as symptomatic or asymptomatic at the initiation of treatment with these two drugs. Twelve patients who had already had apparent symptoms due to heart failure were enrolled in a treatment group. Forty patients who had no symptoms with reduced LV ejection fraction (≤ 45% in echocardiography) were enrolled in a prevention group.

RESULTS

Five-year and 7-year survival rates of all patients were 93 and 84%, respectively. In the treatment group, 5-year and 7-year survival rate were 81 and 71%, respectively. Survival rate became zero at 10.9 years. In the prevention group, 5-year and 7-year survival rates were 97 and 84%, respectively, and 10-year survival rate was 72%. Nine patients in the prevention group remained event-free over 10 years.

CONCLUSIONS

In this study, the combination of an ACE inhibitor and a beta-blocker had a beneficial effect on long-term survival of DMD patients with heart failure. The treatment was particularly effective for asymptomatic patients with LV dysfunction.

Complications of anaesthesia in neuromuscular disorders

The purpose of this review is to alert non-anaesthesiologists to the various complications from which patients with neuromuscular disorders and those susceptible to malignant hyperthermia can suffer during anaesthesia. The patient's outcome correlates with the quality of consultation between anaesthesiologists, surgeons, neurologists and cardiologists. Special precautions must be taken, since many anaesthetics and muscle relaxants can aggravate the clinical features or trigger life-threatening reactions. Complications frequently occur in these patients, although anaesthetic procedures have become safer by the reduced administration of suxamethonium and the use of total intravenous anaesthesia, new volatile anaesthetics and non-depolarising relaxants. This review provides a synopsis of pre-operative anaesthetic considerations and adverse drug effects on skeletal, cardiac and smooth muscle tissue. It describes the pathogenetic aspects of typical complications and introduces anaesthetic procedures for the various neuromuscular disorders, including regional anaesthesia for patients in whom a restriction of respiratory and/or cardiac function is predicted.

Pulsed Doppler tissue imaging in dystrophinopathic cardiomyopathy

Cardiac dysfunction is a primary feature in patients and female carriers of Becker muscular dystrophy (BMD). Conventional echocardiography and pulsed Doppler tissue imaging (DTI) were performed in 28 patients with BMD, in 20 female carriers, and in 38 control participants (20 men and 18 women). Left ventricular ejection fraction (LVEF) was lower in BMD patients (P <.02) and carriers (P <.02) than in normal participants. Two subgroups of BMD patients were identified: A1 = LVEF > or = 55% (n = 20) and A2 = LVEF < 55% (n = 8). The carriers displayed LVEF > or = 55%. Compared with control participants the diastolic alterations by conventional echocardiography were lower early filling peak in the subgroup A1 (P <.05) and prolonged isovolumic relaxation time in A1, A2, and in carriers (at least P <.02). Furthermore, pulsed DTI showed lower early diastolic wave peak at basal septum in A2 (P <.05) and in carriers (P <.0001); at lateral mitral annulus and at basal inferior wall in A1, A2, and in carriers (at least P <.05); lower early/late diastolic wave ratio at basal septum and lateral mitral annulus (P <.05) in carriers; and prolonged isovolumic relaxation time in A1, A2, and in carriers (at least P <.02), except at lateral mitral annulus of carriers. Systolic parameters investigated by pulsed DTI detected lower peak systolic wave at basal septum in A1, A2, and carriers (P <.02); at lateral mitral annulus in carriers (P <.02); at basal inferior wall in A1, A2 (P <.02), and in carriers (P <.0001); and lower time-velocity integral of S wave at each segment in A1, A2, and in carriers. In dystrophinopathic cardiomyopathy, pulsed DTI may be a useful technique to assess diastolic dysfunction and appears to be a promising tool in identifying early regional systolic alterations in patients and carriers with normal LVEF.

Cardioprotection for Duchenne's muscular dystrophy

PURPOSE

To explore the use of neuroendocrine monitoring for more timely diagnosis of dilated cardiomyopathy (DCM) in Duchenne's muscular dystrophy (DMD) and to determine the effects of angiotensin-converting enzyme inhibitors (ACEI) and beta-blockers on neuroendocrine levels, left ventricular diastolic diameter (LVDd), ejection fraction, and mortality rate on DMD.

METHODS

Eighty-five patients with DMD underwent yearly cardiac monitoring including neuroendocrine screening. Eleven patients had symptoms of DCM develop once plasma neuroendocrine levels increased. At this point the patients received ACEI for 9 to 62 months (35.8 +/- 18.4 months) and beta-blockers for 7 to 60 months (31.6 +/- 20.1 months).

RESULTS

The combination of ACEI and beta-blockers relieved symptoms and signs of heart failure in all 11 patients and significantly reduced atrial natriuretic protein (ANP) levels from 197.5 +/- 152.1 pg/mL to 25.5 +/- 16.2 pg/mL ( P <.002) at 15.5 +/- 8.2 months, brain natriuretic protein from 523.8 +/- 434.8 pg/mL to 59.3 +/- 24. 2 pg/mL ( P <.05) at 12.2 +/- 3.1 months (data complete for 5 patients), norepinephrine levels from 1114 +/- 689 pg/mL to 360 +/- 257 pg/mL at 20.5 +/- 9.6 months for 11 patients (P =.001), and LVDd from 65.9 +/- 9.2 mm to 63.3 +/- 6.3 mm (P =.15) at 15.0 +/- 7.4 months for 10 patients, including 3 for whom the LVDd increased by 2 to 6 mm. The combination increased left ventricular ejection fraction (LVEF) from 25.1% +/- 9.2% to 36.5% +/- 5.8% (P <.001) at 17.1 +/- 11.0 months for 10 patients. For 9 of the patients ANP levels remained lower throughout the 36.8 +/- 20.1 month course of the follow-up. Two patients had sudden severe re-elevations of ANP levels just before death from congestive heart failure after 44 and 23 months of therapy, respectively.

CONCLUSION

Neuroendocrine level monitoring can assist in the diagnosis of DCM in patients with DMD. Combination therapy with ACEI and beta-blockers can significantly decrease neuroendocrine activation and LVDd and reverse symptoms and signs of congestive heart failure for patients with DMD.

The management of neuromuscular ventilatory failure

All patients with respiratory impairment have either primarily ventilatory or primarily oxygenation impairment. Patients with neuromuscular conditions fall into the former category but are all too often managed as though they had the latter with oxygen therapy, bronchodilators, chest physical therapy, intermittent positive pressure breathing, and so on. This approach can only hasten respiratory failure and management by tracheostomy-However, it has been reported that with the use of noninvasive respiratory muscle aids, respiratory morbidity and mortality can be prevented for most patients with neuromuscular disease without resort to tracheostomy or even hospitalization.