Print version ISSN 0066-782X
Arq. Bras. Cardiol. vol.98 no.6 São Paulo June 2012 Epub May 15, 2012
Cristina Nádja Muniz Lima De FalcoI, II; Cesar GrupiI; Eduardo SosaI; Maurício ScanavaccaI; Denise HachulI; Sissy LaraI; Luciana SacilottoI; Cristiano F. PisaniI; José A. F. RamiresI; Francisco DarrieuxI
IInstituto do Coração
da Faculdade de Medicina da Universidade de São Paulo, São Paulo;
Mogi Mirim, SP, Brazil
IIClínica Médica Core Vita, São Paulo; Mogi Mirim, SP, Brazil
BACKGROUND: Premature ventricular and
supraventricular complexes (PVC and PsVC) are frequent and often symptomatic.
The magnesium (Mg) ion plays a role in the physiology of cell membranes and
OBJECTIVE:We evaluated whether the administration of Mg Pidolate (MgP) in patients with PVC and PsVC is superior to placebo (P) in improving symptoms and arrhythmia frequency.
METHODS: Randomized double-blind study with 60 consecutive symptomatic patients with more than 240 PVC or PsVC on 24-hour Holter monitoring who were selected to receive placebo or MgP. To evaluate symptom improvement, a categorical and a specific questionnaire for symptoms related to PVC and PsVC was made. Improvement in premature complex density (PCD) per hour was considered significant if percentage reduction was >70% after treatment. The dose of MgP was 3.0 g/day for 30 days, equivalent to 260mg of Mg element. None of the patients had structural heart disease or renal failure.
RESULTS: Of the 60 patients, 33 were female (55%). Ages ranged from 16 to 70 years old. In the MgP group, 76.6% of patients had a PCD reduction >70%, 10% of them >50% and only 13.4% <50%. In the P group, 40% showed slight improvement, <30%, in the premature complexes frequency (p < 0.001). Symptom improvement was achieved in 93.3% of patients in the MgP group, compared with only 16.7% in the P group (p < 0.001).
CONCLUSION: Oral Mg supplementation decreases PCD, resulting in symptom improvement. (Arq Bras Cardiol 2012;98(6):480-487)
Keywords: Arrhythmias, cardiac; ventricular premature complexes; magnesium; ion channels.
Premature ventricular and supraventricular complexes (PVC and PsVC) are frequent and often symptomatic. Their prevalence can occur in up to 50% of the general population, especially1. The incidence of this arrhythmia increases with age2-5. The studies show that most of these patients had <1 PVC per hour, usually monomorphic and single forms2,3.
Symptoms related to PVC and PsVC can be very troublesome or even disabling. Patients may refer to these symptoms as a "skipped beat," "punch in the chest," palpitations, dyspnea, cough, dizziness, atypical chest pain, and near syncope1,6, affecting quality of life. These symptoms are usually noticed when the premature complexe density is high. Premature complexes are directly related to heart cell excitability, which is influenced by electrolyte balance in intracellular fluid. The interaction between magnesium (Mg) and calcium (Ca) has particular relevance in the regulation of nerve and muscle cell permeability7-9, and in the ATPase - Na +/K + pump8,9. By acting on the physiology of cell membranes, Mg has a special role in cardiac rhythm maintenance8,9.
Mg is the second most abundant intracellular cation8,9 and plays an important role in the activity of many coenzymes and ATP-dependent reactions, including membrane-dependent energy transport9,10. Less than1% of magnesium is found in blood9 and only approximately 0.3% in serum11,12. Therefore, the intracellular deficiencies can be underdiagnosed8.
Lifestyles characterized by stress, low micronutrient intake, physical training, sleep deprivation, and the use of certain medications (diuretics, aminoglycosides, and cyclosporine) may lead to Mg deficiency. This ion is mainly found in seeds, nuts, vegetables, and wheat bran. In the general population, magnesium deficiency probably occurs due to low magnesium dietary intake13,14 ,that needs to maintain adequate intracellular values and, in the elderly, by decreasing appetite14.
This study aimed to assess whether oral administration of magnesium pidolate in patients with PVC or PsVC is superior to placebo in improving symptoms and the frequency of premature complex (PC), as well as whether symptom improvement is related to a significant reduction in arrhythmia frequency.
Study Design and Participants
Patients were recruited from the Arrhythmia Unit of the Heart Institute (InCor), University of São Paulo Medical School and Core Vita Clinics. Patients were eligible if they were symptomatic and had more than 240 PVC or PsVC per day on 24h Holter monitoring(or more than 10/hour). Exclusion criteria were impaired renal function, structural heart disease (except mitral valve prolapse without regurgitation), or the use of concomitant drugs. The study was approved by the ethics committees of the participating centers in the study with the number CAPPesq-0613/10.
After providing written informed consent, all trial participants were randomly assigned to receive placebo (P) or magnesium pidolate (MgP), each administered in a blinded manner. All the patients did echocardiogram and none of them had structural heart disease or electrolyte disturbances; the determination of electrolytes( magnesium, sodium, calcium and potassium) and the renal function were normal.
The dose of the MgP was 3.0 g/day for 30 days, which contains 260mg of Mg element. The magnesium, sodium, calcium, and potassium serum dosage was taken at baseline, at 15 days, and at 30 days after randomization.
The 24-hour Holter (3 channels) was performed at baseline and 30 days after the medication use. The count of the premature complexes was performed following the institution protocol and the premature complex density (PCD) was performed dividing the total number of atrial and ventricular extra systoles Holter counted in the number of hours of recording.
Follow-up visits occurred at randomization, after 15 days, and after 30 days.
To evaluate symptom improvement, a specific questionnaire related to PC was made with the following questions:1- Failure or "leaps" in the chest; 2-Couch with palpitations;3-Dizziness;4-Dyspnea:5-Sudoresis and/or chest pain. According to frequency of symptoms was made a "score" (Fig. 1). For this "score", was only considered an improvement, if the patient had a reduction of at least two categories, for example, was in the score IV before treatment and migrated to the score I or II after treatment .Furthermore, it was made a categorical classification of patients with questioning whether there was improvement of symptoms, with only answers "yes" or "no ".
To meet the objectives of the study, we calculated the percentage changes in PCD /hour, and was considered success criteria, after treatment, the percentage reduction >70% per 24-hour Holter. Data are presented using summary statistics (mean, standard deviation, median, minimum, maximum). Outcome variables were compared between groups using a Mann-Whitney test15. The improvement of either PCD or symptoms was described using absolute and relative values. The existence of an association between groups and the improvement of each criterion was performed using Fisher's exact test15. A p value of 0.05 was considered statistically significant. We described the values of magnesium and potassium before medication, and at 15 and 31 days after medication use, according to groups, and also compared the values between groups and moments using analysis of variance with repeated measures and 2 factors16.
A statistical power of 80% was chosen to detect a 60% symptom reduction with MgP and 30% with P, with a confidence interval of 95%.
A total of 60 patients were enrolled in the program between October 2010 and August 2011. Both treatment groups had similar baseline characteristics. The mean age was 46.47 (MgP) to 48.53 (P), and 55% were women (Table 1). Age description and PCD variation according to each group are described in Table 1.The average extra-systole in 24 hours in both groups was higher than 4.955 PC/day. Twelve patients had mitral valve prolapse without insufficiency (5 in group P and 7 in group MgP).
Frequency of Premature Complexes
In the MgP group, 76.6% of patients had a PCD reduction >70%, 10% of them >50% and only 13.4% <50%. In the P group, 40% showed slight improvement, <30%, in the PC frequency and none of them had improvement >70% (Table 2/ Figure 2). Patients in the MgP group had an average reduction of 77.13% (SD = 24.57%) of PCD, whereas the placebo group had an average increase of 47.99% (SD = 158.93%) in PCD (p<0.001) (Table 2/Figure 3). This difference was also consistent for both PVC and PsVC (p<0.001) (Table 2). A few patients (13.4%) had only a slight improvement in PC density in the MgP group (<50% in PC frequency), but had improvement in symptoms.
In the P group, only 16.7% reported symptom improvement (score), whereas in the MgP group there was an improvement of 93.3% (p <0.001) (Table 2). As a categorical variable, there was improvement of symptoms in 93.3% of patients in the MgP, compared with only 13.3% in the placebo group (p <0.001) (Table 2). Figures 4 and 5 show the superiority of symptom improvement in patients receiving MgP compared with patients receiving P.
There were no significant changes in serum magnesium, potassium, sodium and calcium during the study in both groups. Serum magnesium did not differ significantly between groups (p = 0.743) or between periods of time (before and after oral supplementation; p = 0.154); moreover, serum potassium did not differ statistically between groups or during follow-up (p = 0.415, p = 0.804, respectively). Table 2 and Figure 6 illustrate the changes in magnesium.
Study Discontinuation and Adverse Events
Only one patient in the MgP group had to discontinue the protocol after 10 days due to diarrhea, which was promptly resolved within 24 hours.
Oral magnesium supplementation not only decreases the density of premature ventricular and supraventricular complexes, but also improves symptoms compared to placebo. In the placebo group, only 16.7% showed improvement in symptoms compared to 93.3% of patients using MgP. Although most patients have improved PC density and symptoms, some patients have improved symptoms without a significant drop in PC density. The worsening of PCD in some patients in the placebo group can perhaps be explained by the great variability that involves spontaneous idiopathic arrhythmias. However, it is important to note that both groups were subjected to this variability, and even then, there was a statistically significant reduction of PCD in the magnesium group compared with the placebo group.
The mechanisms by which magnesium administration reduces the incidence of PC are not entirely known. Magnesium is regarded as a significant regulator of cardiac cell function. Depletion of magnesium, as shown in some studies, may be proarrhythmic14. Zehender et al17 demonstrated that increased intake of potassium and magnesium in patients with frequent ventricular arrhythmias can result in a moderate but significant antiarrhythmic effect, although the frequency of tachyarrhythmia and symptoms has not been changed17. However, this sample differs from our results, probably because the population is different: most patients had other cardiac co morbidities, and some were using other medications.
On the possibility of oral magnesium overload, it is important to note that patients in the MgP group had a normal Mg serum dosage during the 30-day follow-up, without major adverse effects or the need for suspension (except for a single patient with diarrhea). It is likely that intracellular levels of Mg are low, despite normal serum dosage, since serum dosage corresponds to only 0.3% of total magnesium. It would be interesting to find out minimally invasive, accurate methods to detect intracellular Mg levels18 to better understand many diseases, including cardiac arrhythmias.
There are some studies with fluorescent markers specific to magnesium (and Mg-Fluo-4/AM KMG-20/AM)19, that aim at the cation dosage in various cell types, such as platelets, red blood cells, lymphocytes12, cardiomyocytes (in rats)19 and epithelial sublingual cells18. Silver et al18 showed a significant correlation between the magnesium values in heart muscle biopsies from bypass surgery, with the values measured in sublingual epithelial cell smear. Moreover, magnetic resonance imaging (MRI) is a noninvasive test for tissue Mg analysis. Recently, the Transient Receptor Potential Melastation channel and its role in hypomagnesemia were identified. Chronic Mg deficiency may be explained by changes in these specific membrane transporters12,20,21.
Magnesium is closely related to the maintenance of cellular ionic balance in combination with sodium, potassium, and calcium; it cooperates with the Na +/K+ ATPase pump8,9,14. Magnesium deficiency causes an increase in intracellular Na +, which allows cellular K + loss9. Mg also affects calcium homeostasis, and many calcium channels are magnesium dependent. In addition, Mg is needed for the release and action of parathyroid hormone9.
Some conditions are associated with magnesium deficiency, such as metabolic syndrome22,23, hypertension, congestive heart failure, diabetes, preeclampsia, and arrhythmias, and some clinical studies show that supplementation was beneficial in controlling these diseases14.. A single study showed that 365 mg of magnesium per day for 8 weeks lowers blood pressure24. According to Tong and Rude, magnesium reduces irregular heartbeat, and because intracellular Mg depletion may be present despite a normal serum Mg, magnesium deficiency must always be considered as a potential factor in cardiac dysrhythmias25. In the intensive care unit, magnesium is used when arrhythmias do not respond to conventional medications, and also in digitalis intoxication26. In heart failure, magnesium deficiency is caused by diuretic therapy, which increases the incidence of arrhythmia, among them premature complexes8,14.
The Mg balance among different compartments of the body occurs slowly, so that the concentration of Mg in one tissue does not correspond to that in another12. Less than 1% of total body Mg is present in blood9 and only 0.3% in serum11,12, so serum levels do not reflect the total body stores27,28. This may be one explanation for the improvement of arrhythmia with the replacement of Mg compared to the placebo group, even without changes in serum levels of this ion.
Although symptom improvement could be associated with a reduction in PC density, even in some cases in which this decline is not significant, symptoms also improved. This is partly explained by the placebo effect, as well as magnesium action in nerve cells. A nutrition education rich in magnesium may be a practical alternative for the treatment of this arrhythmia. However, this information must be evaluated in another study. It is also important to control serum Mg during treatment and to assess renal function.
Long-term follow-up was not performed; therefore, it is not possible to establish whether these patients are free from symptom recurrence after oral replacement of magnesium. Intracellular magnesium was not measured, but Mg serum dosages have shown that this replacement was safe and effective. The goal of reduction in the density of premature ventricular and supraventricular complexes and symptom improvement was achieved. The specific symptom score was not validated, because it does not exist in the literature. However, a simple categorical score was also made, with a good correlation between reduced PCD and symptom improvement. Moreover, the aim of this study was not to prevent life threatening arrhythmic events. It shows that the data should not be used as justification for treating patients with this objective, especially those with heart disease.
Simple oral Mg replacement reduced the density of premature ventricular and supraventricular complexes and specially improved symptoms in our study population (no cardiac heart disease).Clinical and molecular studies are needed to evaluate intracellular Mg and develop better targets for the daily needs of this ion, show probable deficiencies, and explain how to prevent and better treat patients with symptomatic premature ventricular and supraventricular complexes and no apparent heart disease.
The authors wish to thank the external collaborators Mrs. Alessandra Manera, Cacilda Motta, and Kérolem Ignatius for their technical support and Prof. Dr. Paulo Sampaio Gutierrez for valuable guidance. And also by the Laboratory Baldacci free supply of medication "Magnesium Pidolate and Placebo"
Potential Conflict of Interest
No potential conflict of interest relevant to
Sources of Funding
There were no external funding sources for this study.
This article is part of the thesis of doctoral submitted by Cristina Nádja Muniz Lima de Falco, from Faculdade de Medicina Instituto do Coração Universidade de São Paulo.
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Manuscript received January 17, 2012; Erratum The version of "Successful Improvement of Frequency and Symptoms of Premature Complexes after Oral Magnesium Administration" published as ahead of print by Arquivos Brasileiros de Cardiologia underwent the following modification as required by the Editor on 10/11/2012: In the Methods section of the Abstract, PsVC/h was replaced by PsVC.
Manuscript revised January 17, 2012;
Accepted March 05, 2012.
Manuscript received January 17, 2012;
The version of "Successful Improvement of Frequency and Symptoms of Premature Complexes after Oral Magnesium Administration" published as ahead of print by Arquivos Brasileiros de Cardiologia underwent the following modification as required by the Editor on 10/11/2012: In the Methods section of the Abstract, PsVC/h was replaced by PsVC.