1. LOW-ENERGY DIETS: AN IMPORTANT CAUSE
FOR ACQUIRED LONG QT SYNDROME AND
UNEXPECTED SUDDEN DEATH
DANIEL B. PETROV, MD, FESC &
MARIA H. MILANOVA, MD, PHD
DEPARTMENT OF CARDIOLOGY,
EMERGENCY HOSPITAL “PIROGOV”, SOFIA,
BULGARIA

2. OBJECTIVE:
To determine whether low-energy diets influence
cardiac repolarization, as indicated by
electrocardiographic QT interval.

3. BACKGROUND:
Low-energy diets might lead to QT interval prolongation,
torsade de pointes and sudden death. Examination of weekly
ECGs of 29 patients on very-low caloric intake for weight
loss demonstrated prolongation of the QTc interval in 20
patients during the seventh week at the end of the fast. The
importance of these findings is illustrated by one patient
reported in the Texas Heart Institute Journal (2003), with
QTc lengthening after fasting who sustained cardiac arrest
due to torsade de pointes, successfully resuscitated.

4. METHODS:
The electrocardiogram, QT, RR and QTc [QT/RR(0,5)]
intervals were assessed in 29 healthy obese (BMI>27
kg/m2) subjects on very low caloric diets (800 kcal/d) for 7
weeks. QT, corrected QTc intervals were measured along
with serum albumin and electrolytes at the beginning, once
weekly and at the end of diet therapy. 12-lead ECG had
been obtained from all patients in supine position after 10
min. at rest, in the absence of QT prolongation drugs. The
ECG were recorded at standard gain (10mV/mm) and
speed (25 mm/s).

5. METHODS:
The QT interval was measured from the onset of the
QRS complex to the end of the T wave in all leads,
where the end of the T wave could be clearly defined and
averaged 3 to 5 beats. All the QT interval measurements
were performed with patients in sinus rhythm. QT
intervals were corrected for heart rate using the Bazett
formula. The patients with atrial fibrillation, bundle
branch block and pacemakers were excluded from the
study.

6. RESULTS:
The QTc interval before the start of diet was 0.42+/-
0.025s by manual measurement and 0.41+/-0.022s by
automated measurement. 20 of the patients showed a
QTc interval of greater than 0.43s, and 12 patients
demonstrated moderate QT prolongation (>0.45s) at the
end of the diet.

7. TABLE 1. CORRESPONDING OF QTC WITH ELECTROLYTES AND SERUM
ALBUMIN LEVELS
start and end of diet
QTc
Electrolytes levels
Serum albumin levels
start of diet end of diet
QTc 0.42+/-0.025s
by manual measurement
0.41+/-0.022s
by automated measurement
9 patients with QTc <0.43s
20 patients with QTc >0.43s and 12
of them with QTc >0.45s;
Patients with QTc >0.45s:
- 4 patients with QTc = 0.48s
- 2 patients with QTc = 0.49s
- 2 patients with QTc = 0.51s
- 1 patient with QTc = 0.52s
- 2 patients with QTc = 0.54s
- 1 patient with QTc = 0.55s
Electrolytes levels normal in all patients normal in all patients
Serum albumin levels normal in all patients normal in all patients

8. CONCLUSIONS:
Low-energy diets are associated with prolongation of the QTc interval. They
represent an important cause for acquired long QT syndrome for the following
reasons:
1. There is a risk of potentially lethal ventricular arrhythmias such as torsade
de pointes, which has been suggested to be related to repolarization
abnormalities such as QT interval prolongation.
2. The patients on low-energy diets required close medical supervision with
ECG assessment and given the fact that these subjects are often young and
otherwise healthy, makes their ECG monitoring all the more critical.
3. QT interval prolongation drugs should be avoided in patients on low-energy
diets.

9. ACKNOWLEDGMENTS:
This study was supported by the
Bulgarian Pharmaceutical Company
Actavis, Sofia, Bulgaria

10. Thank you!