Congenital long QT syndrome in adults

A family with the Romano-Ward syndrome is presented. This family showed typical features of this syndrome with QT prolongation, torsades de pointes ventricular tachycardia, sudden death and an autosomal dominant inheritance pattern. The index case presented with an exacerbation of torsades de pointes ventricular tachycardia from diuretic induced hypokalaemia, and responded to diuretic withdrawal and beta blocker therapy.

Atrial natriuretic peptide levels in congestive heart failure in man before and during converting enzyme inhibition

1. To determine the response of plasma atrial natriuretic peptide (ANP) to treatment with an angiotensin converting enzyme (ACE) inhibitor in heart failure, seven patients (NYHA Functional Class III-IV) were studied before and after the addition of ramipril to maintenance digoxin and diuretic treatment. 2. Baseline arterial ANP levels were raised, but fell during ramipril treatment in parallel with changes in both haemodynamic recordings (arterial pressure, pulmonary artery diastolic pressure, and right atrial pressure) and hormone levels (angiotensin II and aldosterone). 3. Coronary sinus ANP, measured in three patients, was greater than concomitant arterial levels, and the coronary sinus ANP secretion rate was calculated to be between 15 and 119 pmol/min. 4. These results demonstrate that improvement in haemodynamic function during ACE inhibitor treatment is associated with a decline in elevated ANP levels, and support the concept that atrial stretch or pressure regulates the secretion of atrial peptides in man.

The role of selenium deficiency in occidental dilated cardiomyopathy

The whole blood selenium concentrations were measured in 14 consecutive cases of catheter-proven dilated cardiomyopathy. The mean range of selenium was 59 ng/mL (SD 14). Patients with coronary heart disease had a mean value of 44 ng/mL (9.7) and normal controls had 78 ng/mL (20.1). These results would not support the hypothesis that selenium deficiency is an important causative agent in dilated cardiomyopathy in New Zealand.

Chronic and acute volume expansion in normal man: effect on atrial diameter and plasma atrial natriuretic peptide

Plasma levels of immunoreactive alpha human atrial natriuretic peptide (IR-ANP) and left atrial diameter were measured in 6 normal subjects before and after 6 days of sodium loading using salt supplements and 9-alpha-fluorohydrocortisone. During chronic sodium loading, which increased mean body weight by 1.5 kg and markedly reduced plasma renin and aldosterone levels, plasma IR-ANP increased from 21 +/- 3 to 36 +/- 7 pmol/l (P less than 0.02). Increase in atrial diameter correlated with gains in body weight (r = 0.93, P less than 0.01) but not with increase in plasma IR-ANP. After chronic sodium loading for 6 days, further volume expansion (2 litres of saline infused over 2 hours) significantly increased left atrial diameter but did not affect plasma IR-ANP levels. We conclude that chronic sodium loads increase plasma IR-ANP. However, the failure of further acute atrial distension to increase hormone levels suggests that factors in addition to atrial stretch are important in regulating atrial peptide secretion in man.

Automatic implantable defibrillators

The automatic implantable defibrillator was developed in the USA by Mirowski. This device automatically detects ventricular fibrillation or ventricular tachycardia and delivers a low energy (30 J) shock directly to the myocardium via patch electrodes on the epicardial surface or through a combination of a pericardial patch and an endocardial wire. These devices are being implanted in large numbers in the USA and represent a major contribution to the management and refractory ventricular arrhythmias. Unfortunately their high cost has limited their use in this country despite impressive clinical results.

Converting enzyme inhibitors in heart failure

The renin-angiotensin system is activated in heart failure in proportion to the severity of the haemodynamic derangement and to diuretic dose. Angiotensin converting enzyme (ACE) inhibitors reduce circulating levels of angiotensin II and aldosterone and, in some patients, plasma noradrenaline, vasopressin and cortisol. Typically there is potassium retention and a minor increase in plasma potassium, but cumulative sodium balance may increase or decrease depending on pretreatment fluid and haemodynamic status and on policy regarding diuretic dose. Circulatory dynamics usually improve and blood flow to the brain, myocardium and kidneys is preserved. Changes in glomerular filtration rate are dictated by haemodynamic characteristics and, again, by diuretic dose and dietary sodium. There are potential hazards with ACE inhibitor therapy but most problems can be anticipated and avoided. Future trends may include the introduction of ACE inhibitors with or without concomitant diuretic therapy in early cardiac failure, and intravenous ACE inhibition immediately after acute myocardial infartion. Whether the ACE inhibitors will prove more successful than alternative antihypertensive agents in preventing cardiac complications (including heart failure) of hypertension, is an intriguing question.

Cardiac electrophysiological assessment and the natural history of unexplained syncope

There is little data on cardiac electrophysiological assessment and long term follow-up of unexplained syncope from Australasia. We present 94 patients with unexplained syncope who underwent such assessment and followup for an average of 52 months in 92 patients. Of the 94 investigated 57 were male, the average age was 61 years and average number of syncopal episodes prior to study was 8 (minimum 2). Forty-two patients had heart disease. Patients were divided into 3 groups on results of electro physiological testing. Normal (31 patients), group 1 with intermediate abnormalities of sinus node function or atrioventricular conduction (37 patients) and group 2 in whom the abnormalities were felt likely to represent the cause of syncope (26 patients). Abnormalities detected in group 2 were sinus node dysfunction in 12, abnormal atrioventricular nodal conduction in 8, abnormal infranodal conduction in 2, vagal hypersensitivity in 3 and ventricular tachycardia in two. Follow-up for a mean of 52 months was obtained in 92 patients. Recurrent syncope occurred in 37% of the patients. Treatment reduced recurrent syncope to a level approaching statistical significance in group 2 patients (50% to 13%; 0.01 greater than p greater than 0.05) but had little influence on recurrent syncope in group 1 or normal patients. There were 14 deaths over the follow-up period. Mortality was predicted by group 2 electrophysiological abnormality (p less than 0.02) and the presence of heart disease (p less than 0.05) and was not reduced by specific therapy. Sudden death occurred in 3 patients, all with heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor in human pathophysiology

1. Evidence from numerous experiments incorporating central blood volume expansion and changes in sodium status supports atrial stretch as the prime determinant of ANF release. 2. Plasma ANF levels are the result of both secretion and clearance of the peptide. Clearance is altered by a number of factors, including changes in posture in normal man and is probably impaired in disease states with diminished renal and hepatic blood flow. 3. In normal subjects an inverse relationship exists between plasma ANF values and renin-angiotensin-aldosterone system activity. This relationship is lost and replaced by a positive association in heart failure, presumably reflecting the abnormal concurrence of increased atrial stretch and diminished renal perfusion in this condition. Plasma ANF values rise with increasing severity of heart failure and fall with effective treatment. 4. Plasma ANF values are elevated in hypertension and cardiac tachyarrhythmias possibly reflecting raised central venous and atrial pressures. 5. A variety of other disorders may be associated with abnormal plasma ANF values including cirrhosis and the syndrome of inappropriate ADH secretion. 6. Evidence from low-dose infusions of ANF in normal volunteers suggests that the variations in plasma ANF seen in health and disease are sufficient to exert biological effects. 7. The advent of a specific antagonist is needed to provide further insight into the physiological and pathophysiological roles of ANF.

Effect of posture on clearance of atrial natriuretic peptide from plasma

The effect of posture on plasma atrial natriuretic peptide (ANP) levels during a constant iv infusion of the 28-amino acid polypeptide was investigated in 8 normal men. alpha-Human ANP was infused at a constant rate of 0.5 micrograms/min (162 pmol/min) while the men were supine, then erect, and finally when supine again. Plasma ANP levels rose from 10.9 +/- 1.6 (+/- SEM) to 33.3 +/- 2.4 pmol/L after 60 min of constant infusion with the men in the supine position. On standing, plasma ANP increased further to 40.6 +/- 3.4 pmol/L, then fell to 32.2 +/- 2.7 pmol/L with resumption of supine posture. The calculated MCR of ANP fell from a mean of 7.7 to 5.7 L/min on standing, but rose again to 7.6 L/min upon lying down. We conclude that body posture has a significant effect on the rate of clearance of ANP from plasma.

Atrial natriuretic peptide in spontaneous tachycardias

Because anecdotal reports suggest that concentrations of atrial natriuretic peptide are raised during tachycardias, plasma immunoreactive atrial natriuretic peptide concentrations were measured in 34 consecutive patients when tachycardia was diagnosed and again five and 15 minutes after conversion to sinus rhythm. Plasma atrial natriuretic peptide concentrations were raised in all but four patients, and were higher in patients with known heart disease than in those without. The concentrations were higher with ventricular tachycardia than with atrial fibrillation or supraventricular tachycardia, and in acute versus chronic tachycardia. There was only a weak positive relation between ventricular rate and atrial natriuretic peptide (r = 0.31); but there was a closer inverse correlation between atrial natriuretic peptide and systolic arterial pressure (r = -0.60). Conversion to sinus rhythm was associated with a definite fall in plasma atrial natriuretic peptide concentrations. Despite very high baseline concentrations of atrial natriuretic peptide only two patients reported polyuria. It is likely that atrial pressure rather than ventricular rate determines atrial natriuretic peptide release during tachycardia. Despite the absence of polyuria in all but two patients in this study atrial peptides could still contribute to, or cause, the polyuria of tachycardias.

Atrial natriuretic peptides in man

Research on the physiological role of atrial peptides in man is limited, and the potential for these peptides, or more stable analogues, in therapeutics is uncertain. It is clear, however, that plasma levels of immunoreactive atrial natriuretic peptide (IR-ANP) are increased in volunteers taking a high sodium diet, and are elevated in patients with heart failure, chronic renal failure, and primary aldosteronism. There is suggestive evidence that IR-ANP levels are increased also in essential hypertension, although overlap with normotensives is considerable. Injection or infusion of atrial peptides into man results in a diuresis, an increased output of urine electrolytes, a fall in blood pressure and a rise in heart rate, suppression of aldosterone and sometimes of renin also, and stimulation of norepinephrine. In essential hypertensives, urinary effects may be greater than in normotensives. Heart failure patients show a rise in cardiac output and falls in both systemic and pulmonary arterial pressure. Over the next few years and especially if specific antagonists can be developed, the physiologic and pathophysiologic roles of atrial peptides in normal man and in clinical disorders should be clarified. It is possible that stable analogues of atrial peptides will find a place in the treatment of cardiac failure, renal failure, and perhaps hypertension.

Plasma immunoreactive atrial natriuretic peptide levels after subcutaneous alpha-hANP injection in normal humans

The plasma hormone and urine effects of 100 micrograms of alpha-human atrial natriuretic peptide (alpha-hANP) given by subcutaneous (s.c.) injection, were studied in eight healthy male volunteers. A control s.c. injection was administered on a separate day, and the study was single-blind. The peak immunoreactive atrial natriuretic peptide (IR-ANP) level of 29.4 +/- 4.4 pmol/L reached at 5 min was threefold higher than on the control day. Area under the IR-ANP response curve was approximately 1/32 of that after the same dose of alpha-hANP given by intravenous (i.v.) injection. alpha-hANP s.c. injection was not associated with significant effects on plasma renin activity (PRA), plasma aldosterone, or urine electrolyte excretion. It was concluded that only a small percentage of intact alpha-hANP is absorbed into the circulation after s.c. injection. With the dose of peptide and the injection vehicle chosen, alpha-hANP had little or no biological effect.

The pattern of atrial natriuretic peptide release during ventricular tachycardia in man

1. Plasma levels of atrial natriuretic peptide (ANP) are high in many patients with tachycardia, but patterns of release with onset and termination of tachycardia and relationships to haemodynamic recordings are not clear. Blood for ANP measurements was therefore drawn from the coronary sinus, femoral artery and femoral vein, and simultaneous haemodynamic recordings were made in five patients before, during and after induction of stable ventricular tachycardia for 30 min. 2. Tachycardia induced increases in ANP to peak levels, 2.6 to 5.7 times higher than baseline values at 20 min or later, whereas maximum haemodynamic changes, including a rise in pulmonary artery diastolic pressure, were achieved within 4 min. 3. Reversion to sinus rhythm resulted in immediate changes in haemodynamic recordings, whereas ANP levels in arterial and venous plasma fell sluggishly with an apparent half-life of 9.6 and 7 min, respectively. 4. The results support a central role for atrial pressure in determining ANP secretion, but demonstrate a temporal delay between changes in atrial pressure and ANP secretion.

The course of idiopathic dilated cardiomyopathy in New Zealand

The course of dilated cardiomyopathy in New Zealand was studied in 72 cases that were followed up for less than or equal to 10 years after cardiac catheterisation and coronary angiography. Eighty one per cent were male and 86% were white; the remainder were Maori. The mean age of patients at the time of investigation was 50 X 15 years. Most patients were unskilled labourers. The commonest presenting symptom was dyspnoea and the commonest physical sign was cardiomegaly. Mean survival time from first hospital presentation was 85 months; half the deaths were sudden. Factors predicting a poor survival included cardiomegaly, age, arrhythmias, cigarette smoking, and subclinical thiamine deficiency. The syndrome of dilated cardiomyopathy in New Zealand appears to be identical with that seen in other European populations.

Atrial natriuretic peptide in human hypertension

Preliminary reports are that plasma levels of immunoreactive atrial natriuretic peptide (IR-ANP) are higher in essential hypertensive patients than in normotensive controls, and that the urinary response to injected alpha human atrial natriuretic peptide (alpha-hANP) is augmented in essential hypertension. Further, there are reports of positive relationships between IR-ANP levels and arterial pressure. Confirmation is needed, however, with larger numbers of patients and with careful matching of diet electrolytes, age and sex, body posture, time of day, and other factors which may alter release or plasma clearance of atrial peptides. If indeed IR-ANP levels are raised in essential hypertension, it is possible that increased demands on the atria as a consequence of altered left ventricular structure and function lead to augmented secretion of atrial peptides. Whether the observed minor increases in plasma IR-ANP could have biologic effects to oppose pressor systems, to sustain glomerular filtration rate, and to suppress vasoactive hormone secretion, is unclear since the threshold level of IR-ANP which has biologic actions in man, is unknown. Plasma IR-ANP levels are raised in primary aldosteronism, and fall with treatment. These early reports suggest that atrial peptides might play a role in the pathophysiology of primary aldosteronism and perhaps essential hypertension, but much more information is needed.

Acute hemodynamic, hormonal and electrolyte effects of ramipril in severe congestive heart failure

The response to ramipril, 10 and 20 mg on consecutive days, in 9 patients with severe (New York Heart Association functional class III or IV) chronic congestive heart failure was measured. Hemodynamic cannulae were placed more than 2 days before ramipril administration to ensure a stable baseline. Dietary sodium (40 mmol daily) and potassium (80 mmol daily) were constant before and during the study, and maintenance doses of digoxin and furosemide (80 to 1,000 mg daily) were continued unchanged. Ramipril induced pronounced, sustained decreases in angiotensin converting enzyme activity, angiotensin II and aldosterone levels, and a reciprocal increase in plasma renin activity. Plasma catecholamines, antidiuretic hormone and cortisol levels were not altered. Urinary sodium and potassium excretion diminished, plasma sodium decreased and plasma potassium increased. Plasma urea and creatinine levels increased. Ramipril treatment resulted in a decrease in systemic arterial pressure that was sustained for 24 hours, a decrease in heart rate and an increase in cardiac index, but little change in pulmonary artery pressure or right atrial pressure. Three patients were drowsy after ramipril administration, and 1 patient had a marked, temporary reduction in urine output. It was concluded that ramipril is a potent, long-acting angiotensin converting-enzyme inhibitor that is likely to be beneficial in patients with severe cardiac failure.

Flecainide acetate for conversion of acute supraventricular tachycardia to sinus rhythm

The efficacy of intravenous flecainide acetate (maximum 2 mg/kg or 150 mg given at a rate of 15 mg/min) was assessed in patients with acute supraventricular tachycardia (SVT) (within 24 hours). Fifty patients were studied, 46 with spontaneous SVT and 4 with induced SVT at electrophysiologic assessment. Conversion to sinus rhythm was achieved within 45 minutes in 76%: in 25 patients with atrial fibrillation (76% conversion), 15 with atrioventricular (AV) nodal or AV reentrant tachycardia (100% conversion) and 10 with atrial flutter or atrial reentrant tachycardia (40% conversion). Adverse effects were noted in 21 patients (42%): paresthesia in 9, drowsiness in 8, nausea in 2, accelerated ventricular rate in 5, ventricular tachycardia in 1, sinus bradycardia in 1 and hypotension in 5. Adverse effects were associated with larger dosage and atrial flutter or atrial reentrant tachycardia. Thus, flecainide acetate is effective in converting to sinus rhythm acute atrial fibrillation and AV nodal and AV reentrant tachycardias, but not atrial flutter or atrial reentrant tachycardia.

Haemodynamic effects of atrial peptide infusion in heart failure

The effect of a synthetic analogue of atrial natriuretic peptide (Ileu-ANP) on haemodynamic, hormonal, and electrolyte excretion indices was studied in 7 patients with chronic congestive heart failure. Patients received in random order placebo or Ileu-ANP infusions (5 micrograms/min) for 4 h on 2 separate occasions, at least 1 week apart. Compared with placebo, Ileu-ANP caused significant reductions in mean systemic arterial pressure, mean pulmonary artery pressure, pulmonary diastolic pressure, and right atrial pressure. These changes were sustained for at least 2 h after infusion. Cardiac output increased from 6.2 to 7.4 l/min at 60 min, then returned to pre-infusion levels. Despite considerable falls in systemic pressure there was no significant increase in heart rate or plasma noradrenaline. With Ileu-ANP infusion, plasma renin activity, angiotensin, arginine vasopressin, aldosterone, and cortisol values were not significantly different from placebo values. Plasma cortisol and aldosterone increased after stopping Ileu-ANP. Neither urine volume nor sodium excretion rate was significantly increased by Ileu-ANP.

Atrial natriuretic peptide in humans. Production and clearance by various tissues

Although it is assumed that the human heart secretes atrial peptides, direct proof is not available. We therefore measured immunoreactive atrial natriuretic peptide levels in coronary sinus blood and simultaneously in femoral arterial and venous blood from patients before and during stepwise incremental atrial pacing of up to 200 beats per minute. Since the fate of circulating atrial peptides is unknown, we also measured immunoreactive atrial natriuretic peptide concentrations in arterial and venous blood across the liver, kidney, lower limb, and lung in patients undergoing cardiological investigation. Peptide levels in coronary sinus blood were higher than in samples from the femoral artery or vein. As the heart rate was accelerated by atrial pacing, peptide concentrations increased in coronary sinus blood and to a lesser extent in peripheral samples. Whereas the levels in venous blood draining the liver, kidney, and lower limb were approximately 50% of those in arterial blood, concentrations were similar in samples drawn simultaneously from the pulmonary artery and the aorta. These results show that the human heart produces immunoreactive atrial natriuretic peptide and that secretion increases with atrial tachycardia. The liver, kidney, and lower limb remove the peptide from arterial blood, but there is little change in its concentration during circulation of blood through the lungs.