Notched T waves in young persons with central nervous system lesions

Pseudo-double T wave ECG artifact

In the ECG of a diabetic patient without coronary artery disease, a double T wave was observed. The ECG was normal the next day. This finding was interpreted as representing repolarization abnormalities (e. g., myocardial ischemia) by many health care workers. However, it represents an artifact called "pseudo double T wave". The cause is unknown but most likely due to abnormalities at the interface between surface electrodes and skin tissue. The diagnosis of ECG artifacts requires meticulous examination of the tracings coupled with a thorough knowledge of normal patterns.

Bifid T waves in leads V2 and V3 in children: a normal variant

Introduction

The T wave is rarely bifid, apart from patients with long QT syndrome or subjects treated with antiarrhythmic drugs. At times, a U wave partially superimposed upon the T wave is responsible for an apparently bifid T wave. Bifid T waves, in contrast, have been described in normal children in the past, but the phenomenon has not received any attention in recent years, to the extent that it is not mentioned in current textbooks of paediatric cardiology. Aim of the present study was to determine the incidence and clinical counterpart of bifid T waves in a paediatric population.

Methods

We selected 604 consecutive children free from clinically detectable heart disease; subjects whose electrocardiogram showed a bifid T wave underwent a complete clinical and echocardiographic examination. In addition, the electrocardiograms of 110 consecutive adults have also been analyzed. A T wave was considered as bifid whenever it was notched, being the 2 peaks separated from each other by a notch with duration ≥ 0.02 sec and voltage ≥ 0.05 mV. Moreover, in 7 children with bifid T wave in lead V2 further precordial recordings were obtained: a small electrode was gradually moved from V1 to V3, and 4 additional leads were recorded: 2 between V1 an V2, and 2 between V2 and V3.

Results

A bifid T wave was observed in 110 children (18,3%), with a relatively age-related incidence; the highest rate of bifid T waves (53%) occurred in the group of 5-year-old children. The bifid T wave was detected only in lead V2 in 51 cases (46,4%), only in lead V3 in 5 cases (4,6%), in both leads V2 and V3 in 50 cases (45,4%), and in leads other than V2 and V3 in 4 cases (3,6%). In the adult group, none of the examined electrocardiograms showed bifid T waves in any lead.

In the bifid T wave paediatric population, the echocardiogram did not reveal any abnormality, apart from 3 subjects which had an asymptomatic mitral valve prolapse; a trivial mitral and/or tricuspid regurgitation detected by color Doppler, as well as a patent foramen ovale in infants, were not considered as abnormal findings. The QTc interval was normal in all of the subjects; the average QTc interval was not different in the bifid T wave population (402 ± 46 msec) with respect to the control group (407 ± 39 msec).

Conclusion

The incidence of bifid T waves in leads V2 and V3 in normal children is high, and awareness of this phenomenon avoids possible misinterpretations leading to a diagnosis of ECG abnormalities.

A case of hypocalcemia, heart failure and exceptional repolarization disturbances

Little attention has been given to the question whether clinical heart failure can be a manifestation of hypocalcemia. A patient with hypoparathyroidism and heart failure prompted us to analyse the reports on this subject. The conclusion was that if associated with an underlying myocardial disease, hypocalcemia may be a rare contributing factor to hear failure. Hypocalcemic heart failure without coexisting heart disease has been suggested as a cause of hypotension in two special situations in which a sudden fall of serum ionized calcium is induced: massive transfusions of citrated blood and rapid correction of uremic acidosis. In addition to hypocalcemia and heart failure, our patient had exceptional repolarization disturbances: rate-dependent variation of T wave amplitudes during sinus arrhythmia and unexpected prolongations of the Q-T interval with attacks of ventricular tachycardia.

Prominent bifid T waves observed in the QT prolongation caused by complete atrioventricular blockade in a hypokalemic diabetic patient

A 63-year-old diabetic man was admitted with general fatigue. Electrocardiogram (ECG) on admission showed complete atrioventricular (AV) blockade associated with prominent bifid T waves. The second component of the bifid T waves was distinguished from U waves by the beat-to-beat varying bifidity and the nadir between the two components located at > or = 1 mm above the isoelectric line. Range of absolute QT interval was 535 to 650 ms. Hypokalemia (3.6 mEq/L) was noted at admission. Partial restoration of the potassium level (3.9 mEq/L) prior to temporary ventricular demand pacing obscured the bifid T waves and attenuated the QT prolongation and dispersion to some extent (absolute QT interval ranging 520 to 620 ms). It was concluded that marked bradycardia caused by complete AV blockade (ie, a junctional escaped rhythm at a rate of 42 beats/min), hypokalemia, and underlying diabetes mellitus contributed in concert to the QT prolongation and dispersion leading to the prominent bifid T waves.

T wave "humps" as a potential electrocardiographic marker of the long QT syndrome

OBJECTIVES

This study attempted to determine the prevalence and electrocardiographic (ECG) lead distribution of T wave "humps" (T2, after an initial T wave peak, T1) among families with long QT syndrome and control subjects.

BACKGROUND

T wave abnormalities have been suggested as another facet of familial long QT syndrome, in addition to prolongation of the rate-corrected QT interval (QTc), that might aid in the diagnosis of affected subjects.

METHODS

The ECGs from 254 members of 13 families with long QT syndrome (each with two to four generations of affected members) and from 2,948 healthy control subjects (age > or = 16 years, QTc interval 0.39 to 0.46 s) were collected and analyzed. Tracings from families with long QT syndrome were read without knowledge of QTc interval or family member status (210 blood relatives and 44 spouses).

RESULTS

We found that T2 was present in 53%, 27% and 5% of blood relatives with a "prolonged" (> or = 0.47 s, "borderline" (0.42 to 0.46 s) and "normal" (< or = 0.41 s) QTc interval, respectively (p < 0.0001), but in only 5% and 0% of spouses with a borderline and normal QTc interval, respectively (p = 0.06 vs. blood relatives). Among blood relatives with T2, the mean [+/- SD] maximal T1T2 interval was 0.10 +/- 0.03 s and correlated with the QTc interval (p < 0.01); a completely distinct U wave was seen in 23%. T2 was confined to leads V2 and V3 in 10%, whereas V4, V5, V6 or a limb lead was involved in 90% of blood relatives with T2. Among blood relatives with a borderline QTc interval, 50% of those with versus 20% of those without major symptoms manifested T2 in at least one left precordial or limb lead (p = 0.05). A T2 amplitude > 1 mm (grade III) was observed, respectively, in 19%, 6% and 0% of blood relatives with a prolonged, borderline and normal QTc interval with T2 in at least one left precordial or limb lead. Among the 2,948 control subjects, 0.6% exhibited T2 confined to leads V2 and V3, and 0.9% had T2 involving one or more left precordial lead (but none of the limb leads). Among 37 asymptomatic adult blood relatives with QTc intervals 0.42 to 0.46 s, T2 was found in left precordial or limb leads in 9 (24%; 5 with limb lead involvement) versus only 1.9% of control subjects with a borderline QTc interval (p < 0.0001).

CONCLUSIONS

These findings are consistent with the hypothesis that in families with long QT syndrome, T wave humps involving left precordial or (especially) limb leads, even among asymptomatic blood relatives with a borderline QTc interval, suggest the presence of the long QT syndrome trait.

Changes in T wave morphology during hypercalcemia and its relation to the severity of hypercalcemia

The effect of hypercalcemia on T wave morphology, polarity, and amplitude was studied in 14 patients with a primary diagnosis of malignant lymphoma (8 patients), adult T-cell leukemia (5 patients), and Hodgkin's disease (1 patient). Hypercalcemia was severe to extreme in 11 (14.9-22.8 mg/dl), moderate in 1 (13.4 mg/dl), and mild in 2 (11.8 and 12.2 mg/dl) patients. Ten of the 11 patients (91%) with severe hypercalcemia showed inverted, biphasic, and notched T waves, mainly in the chest leads. Notched T waves were observed in all 10 of these patients in anterior to lateral, mid to lateral, or lateral chest leads. Biphasic and/or inverted T waves in anterior or anterior to midchest leads were present in 4 of these 10 patients who had extreme hypercalcemia (greater than 16 mg/dl). Changes in T wave morphology were not observed in moderate or mild hypercalcemia. T wave amplitude showed significant inverse correlation with serum calcium (T mV vs Ca, r = -0.60, p less than 0.001; T/R ratio vs Ca, r = -0.68, p less than 0.001; n = 35). Decrease in T wave amplitude was marked in severe hypercalcemia (p less than 0.0001) and moderate hypercalcemia, but there was no change in mild hypercalcemia. Changes in T wave morphology, polarity, and amplitude either appeared with development of hypercalcemia or disappeared with normalization of serum calcium level. It was concluded that in addition to shortening the QT interval, severe to extreme hypercalcemia can cause development of inverted, biphasic, or notched T wave with a marked decrease in amplitude of T waves.

Cardiovascular regulation and lesions of the central nervous system

The central nervous system has an important role in the second-to-second regulation of cardiac activity and vasomotor tone. Central lesions that lead to a disturbance in autonomic activity tend to cause electrocardiographic and pathological evidence of myocardial damage, cardiac arrhythmias, and disturbances of arterial blood pressure regulation. To a great extent such cardiovascular disturbances result from alterations in sympathetic activity. Similar alterations in sympathetic activity can occur under conditions of emotional stress and precipitate cardiac arrhythmias that can themselves lead to the syndrome of sudden death. Experimental and clinical evidence suggests that central neural mechanisms may be involved in this important human syndrome, but no central lesion has yet been identified to account for it. Recent experimental evidence, derived from hypertension research, suggests that chemical disturbances in the central nervous system, without accompanying structural lesions, may be found to explain cardiovascular disturbances such as sudden death and hypertension.

Clinical electrocardiographic studies of bifid T waves

In 129 electrocardiograms from 129 patients showing bifid T waves as well as U waves the intervals from the beginning of the QRS complex to the two T wave apices (QaT1, QaT2), to the end of the T wave (QeT), and to the apex of the U wave (QaU) were measured. Eighty additional electrocardiograms from matched control subjects showing single peaked T waves were also studied. The precordial distribution of bifid T waves was assessed by calculating lead prevalence indices. This index progressively increased from 2.15 in the age range 20-29 years to 3.72 in the age range 60-69 years, and was significantly higher in patients with left ventricular hypertrophy and ischaemia (4.04) than in those with otherwise normal electrocardiograms (2.35). Thus older age and left ventricular pathology were accompanied by a more leftward location of bifid T waves. Exercise accentuated the bifid nature of the T wave in 12 of 18 patients with otherwise normal electrocardiograms, and diminished it in 11 of 19 cases with left ventricular hypertrophy and ischaemia. When 41 otherwise normal tracings showing bifid T waves were compared with those of 42 matched controls showing single peaked T waves, the QTc was longer and the eTaU interval shorter in the group with bifid T waves. Similarly, 40 patients with left ventricular hypertrophy and ischaemia showing bifid T waves had longer QTc and shorter eTaU intervals than 38 patients with the same diagnosis with single peaked T waves. These findings suggest that right precordial bifid T waves in younger patients with otherwise normal electrocardiograms probably result from delayed right ventricular repolarisation, whereas left precordial bifid T waves in older patients with left ventricular hypertrophy and ischaemia may indicate repolarisation delay in the ischaemic left ventricle.

The genesis of bifid T waves: experimental demonstration in isolated perfused rabbit hearts

In an attempt to elucidate the genesis of bifid T waves, we recorded transmembrane potentials of subepicardial ventricular muscle fibers simultaneously with a bipolar ventricular electrogram in isolated, perfused rabbit hearts, and the timing of the two apices of the T wave (aT1, aT2) was correlated with ventricular repolarization. The following results were obtained. (1) In seven of the nine hearts in which the repolarization process was mapped on the anterior and posterior surfaces of both ventricles, the 80% repolarization times of the left and the right ventricles were scattered around aT1 and aT2, respectively, and their average values closely corresponded to Q-aT1 and Q-aT2 intervals. This suggested that aT1 and aT2 depended on repolarization of the left and the right ventricles, respectively. (2) In one heart, aT1 appeared to reflect repolarization of the posterior ventricular wall, and aT2 that of the anterior wall. (3) In the remaining heart, aT2 coincided with repolarization of the anterobasal portion of the right ventricle, and aT1 that of the remaining portions of the ventricles. Even when ventricular repolarization was modified by low K+, low Ca2+ or procainamide perfusion, or by premature atrial stimulation, the close temporal correlation of the left and right ventricular repolarization with the two apices of the T wave was maintained. Selective cooling of the perfusate in either the left or the right coronary artery resulted in the production of bifid T waves in which aT2 coincided with the delayed repolarization of the cooled ventricle. We conclude that either physiologically or pathologically delayed repolarization in certain portions of the ventricles is most likely the cause of bifid T waves.

Coexistence of pupillary and heart sympathergic asymmetries in cluster headache

Ten cluster headache patients and 10 healthy controls were subjected to electrocardiographic and pupillometric procedures in a search for cardiac and pupillary sympathergic asymmetry. Sympathergic stimulation was provoked by hyperventilation and by instilling tyramine into both eyes. In the control group, hyperventilation changed neither the T-wave form and polarity nor the QTc. Tyramine provoked an equal mydriasis on the two sides. In cluster headache sufferers, hyperventilation produced changes in the T-wave form and polarity as well as an increase of the QTc due to a disproportionate shortening of the R-R and Q-T intervals. An unequal mydriasis was noted after tyramine instillation due to less marked response on the symptomatic side. The observed electrocardiographic abnormalities are considered an expression of an asynchronous repolarization attributed to a sympathergic asymmetry. It is postulated that both the cardiac and pupillary sympathetic imbalance associated with cluster headache are central in origin.

Autonomic dysfunction in polyneuropathies: a report on 106 cases

Autonomic dysfunction is a common feature in various forms of polyradiculoneuropathy. This study investigated the kinds and frequency of of autonomic dysfunction in 106 cases. Denervation insufficiency of organs associated with supersensitivity of reflex mechanisms was found to be the best explanation of the pathophysiology. Early insertion of a transient cardiac pacemaker is recommended to counteract life-threatening cardiac failure.

A study of ECG abnormalities and myocardial specific enzymes in patients with subarachnoid haemorrhage

Twenty-two patients with subarachnoid haemorrhage were investigated for changes in myoglobin, total CK, CK-MB and CK-BB in serum and for the incidence of ECG abnormalities. Serial ECG's showed abnormalities in 20 patients; 15 of these had T wave changes, 15 Q-Tc prolongation, ten had S-T depression and nine U waves and in seven cases arrhythmias were found. The purpose of the study was to find out whether a relationship could be established between the ECG abnormalities and changes in serum myoglobin and enzymes. However, in no patient could myoglobin or enzyme patterns consistent with acute myocardial or cerebral damage be observed and therefore the ECG abnormalities do not seem to be related to detectable myocardial damage.

Significance of minor ST segment and T wave changes in the resting electrocardiogram of asymptomatic subjects

Sixteen thousand resting electrocardiograms were performed on 14000 United Kingdom professional aircrew and air traffic control officers over a two-year period; 103 asymptomatic men with minor ST segment and T wave changes at rest were assessed by exercise electrocardiography and 19 responded abnormally. Five subjects had proven coronary artery disease, one hypertrophic obstructive cardiomyopathy, and one left ventricular dilatation on echocardiography. Eleven subjects were not investigated, of whom three had strongly positive exercise responses. One subject had a false positive response and assuming a false negative response of less than 2 per cent, then a sensitivity of 80.0 per cent, a specificity of 89.1 per cent, a predictive value for the exercise electrocardiogram of 44.46 per cent and for the resting electrocardiogram of 7.8 per cent is obtained. T wave changes induced by hyperventilation were common (53.4% of all). Ten (18.2%) subjects with hyperventilation-induced T wave changes responded abnormally to exercise, three having angiographically proven coronary artery disease lending little support to the contention that the two entities rarely coexist. In spite of the low return from routine electrocardiograms in a population with a low prevalence of coronary artery disease, three-eighths of those with significant coronary artery disease presented with minor ST segment and T wave changes on their resting electrocardiograms.

Significance of primary T wave aberrations in the electrocardiogram of asymptomatic young men. Part 1. Electrocardiographic data

The electrocardiogram (ECG) at rest and during orthostasis and exercise in 51 healthy men 18-19 years of age without history or symptoms of heart disease, but with T wave aberrations in the ECG (group T) were compared to the normal ECGs of 112 controls of the same age. These aberrations (which literature suggests to be due to organic heart disease) consisted of either a notch in the T wave, especially in the midprecordial leads, that sometimes became inverted, or a low T wave without concomitant ST depression. The T wave aberrations at rest in group T were similar to what 25% of the controls evidenced during orthostasis (group B). Both group T and group B had signs of increased sympathetic tone at rest with a higher heart rate and systolic blood pressure than did the subjects with normal ECG both at rest and during orthostasis. These T wave aberrations disappeared for the majority during exercise. Both group T and group B had prolonged QTc intervals. Group T had increased R wave amplitudes which did not correlate to the severity of the T wave aberration or to systolic blood pressure. Our opinion is that primary T wave aberrations in the majority of these young men were because of increased sympathetic tone.

On the mechanism of sudden death with subarachnoid hemorrhage

The mechanism of death in some patients with subarachnoid hemorrhage is cardiac arrhythmia. Prevention of cardiac arrhythmias by suitable drugs might save the life of patients whose brain is still good.

Mimics of coronary heart disease

Numerous disorders can mimic chronic coronary disease either clinically or electrocardiographically. Particularly noteworthy are Wolff-Parkinson-White syndrome, asymmetric septal hypertrophy, floppy mitral valve syndrome, angina pectoris with normal coronary arteries, hyperventilation syndrome, neurogenic T wave abnormalities, vasoregulatory abnormality, cervicoprecordial angina, hyperkalemia or hypokalemia, left ventricular hypertrophy, and left anterior fascicular block.

Effects of bilateral and unilateral stellate stimulation on canine ventricular refractory periods at sites overlapping innervation

The efffects of unilateral right, unilateral left, and bilateral stellate stimulation on ventricular refractory periods at sites of overlapping cardiac sympathetic innervation were studied in 11 pentobarbital anesthetized dogs. The stellates were stimulated with 10 Hz pulses 4 msec in duration with intensities strong enough to produce T wave changes in a vertical ECG lead and just below the intensity at which control of drive of the ventricle at a 400-msec cycle length was lost. Refractory periods shortened more with left stellate stimulation, 17.8 +/- 5.9 msec (mean +/- SD) than with right stellate stimulation, 10.3 +/- 5.1 msec, P less than 0.001. During bilateral stimulation, shortening of refractory periods was no greater whether stimulation was applied first to the left and then right stimulation was added, 19.7 +/- 6.9 msec, or the stimulation was applied first to the left and then right stimulation was added, 18.3 +/- 6.5 msec. The shortening of refractory periods with bilateral stellate stimulation was not significantly different from that with left stellate stimulation alone. The results of this study suggest that ventricular recovery properties in areas of overlapping cardiac sympathetic innervation are less influenced by increases in tone of the right sympathetics than by increases in left sympathetic tone. In addition, the findings indicate that a bilateral increase in cardiac sympathetic tone has no greater effect on recovery properties than the effects of the left cardiac sympathetics alone.

Cardiac abnormalities in a female patient with hypogonadotropic hypogonadism with anosmia

Hypogonadotropic hypogonadism with anosmia was found in a 38 year old female. Cardiac abnormalities were manifested by a second degree heart block as well as a conduction delay below the AV node. Striking T wave inversions developed in the absence of any symptoms. These changes probably reflect a central nervous system defect.

Cardiac abnormalities in subarachnoid hemorrhage: a resumé

There have been numerous reports demonstrating electrocardiographical changes secondary to subarachnoid hemorrhage, consisting of atrial and ventricular arrhythmias, alterations in QRS configuration, Q-T interval prolongation, T-wave abnormalities, and S-T segment elevation or depression. Abnormalities of cardiac muscle and subendocardial hemorrhage have been seen in patients dying of subarachnoid hemorrhage. Experimental work has shown that electrical impulses in the sympathetic nervous system and hypothalamus produce most of these changes, and the implication is that these changes can be prevented by sympathetic blockade. Pulmonary edema also has been shown to occur frequently after subarachnoid hemorrhage, and again the sympathetic nervous system is implicated in the pathophysiology. Studies done illustrating these points are discussed and conclusions drawn with reference to therapy.