Inappropriate sinus tachycardia
Inappropriate sinus tachycardia | |
---|---|
Other names | IST |
ECG of 33-year-old female showing sinus tachycardia at 132 bpm | |
Specialty | Cardiology |
Symptoms | Palpitations, Chest pain, Fatigue, shortness of breath, Lightheadedness, and syncope.[1] |
Causes | Increased sympathetic or decreased parasympathetic drive, increased intrinsic heart rate, dysfunctional neurohormonal modulation, ectopic sinus node activity, and beta-adrenergic receptor autoantibodies. |
Diagnostic method | Persistent or recurrent sinus tachycardia on a 12-lead electrogram or long-term monitoring that is not explained by other means |
Differential diagnosis | Metabolic myopathies, Postural orthostatic tachycardia syndrome, Sinus node reentry, and Vasovagal syncope. |
Treatment | Medications, lifestyle modifications, surgical sinus node exclusion, and sinus or AV node radiofrequency catheter ablation. |
Medication | Ivabradine and Beta-Blockers. |
Frequency | 1.16% in the general population |
Inappropriate sinus tachycardia (IST) is defined as sinus tachycardia that is not caused by identifiable medical ailments, a physiological reaction, or pharmaceuticals (a diagnosis of exclusion) and is accompanied by symptoms, frequently invalidating and affecting quality of life.[2] IST symptoms include palpitations, chest discomfort, exhaustion, shortness of breath, presyncope, and syncope.[1]
While
Signs and symptoms
Causes
The exact cause of Inappropriate sinus tachycardia is still being debated and remains unknown. Several mechanisms have been suggested, including increased sympathetic or decreased parasympathetic drive, increased intrinsic heart rate, dysfunctional neurohormonal modulation, ectopic sinus node activity, and beta-adrenergic receptor autoantibodies. Some data show an abnormal response to autonomic stimulation as a result of tissue/cell level changes (intrinsic mechanism), whereas others show a disruption of the autonomic stimulation itself with normal tissues/cell level findings (extrinsic mechanism). It is possible that both mechanistic theories are correct because, despite sharing a single common pathway of sinus tachycardia, individual patients' underlying mechanistic etiologies may differ.[8]
Mechanism
Over 15 electrical currents tightly control the
Diagnosis
Inappropriate sinus tachycardia is diagnosed when there is persistent or recurrent sinus tachycardia on a 12-lead electrogram or long-term monitoring that is not explained by other means. Invasive testing, such as electrophysiology studies, are not helpful in making the diagnosis, but they may be useful in ruling out a concomitant supraventricular tachycardia mechanism.[3] Inappropriate sinus tachycardia is a diagnosis of exclusion that is rarely made in an asymptomatic patient.[2]
The following criteria are commonly used to define inappropriate sinus tachycardia:[10]
- The axis and morphology of the P wave during tachycardia similar to or identical to that experienced during sinus rhythm
- A resting heart rate of 100 beats per minute or an increase in heart rate of 100 beats per minute with minimal exertion
- Excluding any potential secondary causes of sinus tachycardia
- Ruling out atrial tachycardias
- Palpitations or presyncope (or both) symptoms that have been clearly linked to resting or easily induced sinus tachycardia.
Secondary causes of sinus tachycardia must be ruled out and corrected if present. A full endocrinology evaluation for disease entities such as hyperthyroidism, pheochromocytoma, and diabetes mellitus with evidence of autonomic dysfunction should be included in the evaluation for inappropriate sinus tachycardia.[10]
Differential diagnosis
Inappropriate sinus tachycardia is primarily a diagnosis of exclusion.[7] Upon exertion, an inappropriate heart rate response of sinus tachycardia can be seen in some inborn errors of metabolism that result in metabolic myopathies, such as McArdle disease (GSD-V)[11][12] and hereditary myopathy with lactic acidosis (Larsson–Linderholm syndrome).[13][14]
Sinus tachycardia is a feature of both postural orthostatic tachycardia syndrome and Inappropriate sinus tachycardia. In POTS, there's an abnormal response by the autonomic nervous system when standing up. POTS symptoms are most common when the patient is upright. POTS syndromes and inappropriate sinus tachycardia may overlap, raising the possibility of shared mechanisms. The most common symptoms of POTS are dizziness and, on occasion, syncope, which are also common in IST.[2]
Treatment
Inappropriate sinus tachycardia is a chronic medical condition that has a negative impact on one's quality of life. There are numerous treatment options available, which are frequently combined with nonpharmacologic lifestyle and dietary changes. It is frequently advised to avoid triggers or stimulants such as caffeine, nicotine, and alcohol.[7]
Managing inappropriate sinus tachycardia, controlling symptoms and decreasing rate, remains a significant challenge, especially given the ambiguity of the syndrome itself. Controlling the heart rate, on the other hand, does not always result in the elimination of symptoms. Controlling sinus rate in asymptomatic IST patients is debatable given that the treatment may be worse than the syndrome itself. In IST, no single therapy completely and effectively reduces heart rate and symptoms, which is likely due to the problem's complexity and a lack of a complete understanding of the causes.[3]
In most patients, sleeping with the head of the bed elevated and increasing
Pharmacologic therapy for Inappropriate sinus tachycardia patients should be started gradually, with the goal of lowering HR and improving symptoms. The pharmacologic treatment of IST is empirical, with a trial-and-error approach typically employed.[15]
Other drugs, such as sympatholytics and cholinesterase inhibitors like pyridostigmine, have very limited clinical evidence. There have been no randomized controlled trials regarding the use of these drugs in the treatment of Inappropriate sinus tachycardia, and all, with the possible exception of β-blockers, should be considered off-label indications.[15]
Ivabradine has been shown to reduce HR, improve exercise capacity quantitatively, and reduce subjective symptom burden. The drug appears to have a lower proarrhythmic risk and is well tolerated. Ivabradine shows great promise as the possible therapy of choice for beta-blocker intolerant or suboptimally responsive patients with a chronic condition that frequently becomes clinically problematic in management.[16]
There are no specific guidelines in place to determine which patients with inappropriate sinus tachycardia should be considered for invasive treatments. Interventions to treat inappropriate sinus tachycardia range from surgical sinus node exclusion to sinus or AV node radiofrequency catheter ablation, which typically is followed by permanent pacemaker implantation and, in recent years, radiofrequency sinus node modification.[17]
Several clinical trials have described sinus node modification or ablation in Inappropriate sinus tachycardia. Primary success rates are generally good, however, there is a high rate of symptom recurrence and significant complication rates. These complications include the need for permanent pacing, transient superior vena cava syndrome, and temporary or permanent paralysis of the phrenic nerve. Furthermore, sinus node modification or ablation may not alleviate all IST-related symptoms. There is also no consensus on the best approach, which includes modifications or ablation, open chest versus conventional intravascular access, and mapping methods. Finally, there has been no evidence of symptomatic improvement over time.[18]
Outlook
IST has a generally benign prognosis. One possible reason for a favourable prognosis is that, while IST patients have faster heart rates, their heart rate slows slightly during sleep as well as during various diurnal patterns. Long-term consequences are few, but published studies are small, follow-up is limited, and populations are varied. Although there have been isolated reports, IST is rarely associated with tachycardia-induced cardiomyopathy.[3] Symptoms may last for years but tend not to progress and may eventually fade away.[19]
Epidemiology
Inappropriate sinus tachycardia, defined as 24-hour average HR > 90 bpm and HR > 100 bpm in a supine or sitting position, has a prevalence of 1.16% in the general population.[20] The epidemiology of Inappropriate sinus tachycardia is not well understood. IST can occur at any age, but it is most common in adolescents and young adults.[2] Inappropriate sinus tachycardia was previously thought to be a rare condition affecting young women, with health professionals being overrepresented. This characterization may better define the group of IST patients who are most symptomatic and/or likely to seek medical attention, as opposed to the entire cohort of Inappropriate sinus tachycardia patients.[19]
In IST, the most common comorbidities are psychiatric, including a history of depression in 25.6% as well as anxiety in 24.6%. Higher rates of diabetes mellitus, hypertension, and hypothyroidism have been identified in those with IST, though lower rates of hyperthyroidism have been observed. 28.2% of patients reported an event or physical condition preceding the onset of IST symptoms. Pregnancy was the most common identifiable initiating factor in IST patients (7.9%).[21]
See also
- Supraventricular tachycardia
- Sinus tachycardia
- Postural orthostatic tachycardia syndrome
- Dysautonomia
- Metabolic myopathies
References
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- PMID 35140027. Epub 2022 Feb 6.
- ^ Wakelin A (2017). Living With McArdle Disease (PDF). IAMGSD (International Association of Muscle Glycogen Storage Disease). p. 15.
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Further reading
- Yusuf S, Camm AJ (June 2005). "Deciphering the sinus tachycardias". Clinical Cardiology. 28 (6): 267–276. PMID 16028460.
- Leon H, Guzman JC, Kuusela T, Dillenburg R, Kamath M, Morillo CA (January 2005). "Impaired baroreflex gain in patients with inappropriate sinus tachycardia". Journal of Cardiovascular Electrophysiology. 16 (1): 64–68. S2CID 21822803.
- Sánchez-Quintana D, Cabrera JA, Farré J, Climent V, Anderson RH, Ho SY (February 2005). "Sinus node revisited in the era of electroanatomical mapping and catheter ablation". Heart. 91 (2): 189–194. PMID 15657230.
- Cruz Filho FE, Maia IG, Fagundes ML, Boghossian S, Ribeiro JC (March 1998). "[Sinus node modification by catheter using radiofrequency current in a patient with inappropriate sinus tachycardia. Evaluation of early and late results]" [Sinus node modification by catheter using radiofrequency current in a patient with inappropriate sinus tachycardia. Evaluation of early and late results]. Arquivos Brasileiros de Cardiologia (in Portuguese). 70 (3): 173–176. PMID 9674178.
- Hou, Cody R; Olshansky, Brian; Cortez, Daniel; Duval, Sue; Benditt, David G (2022-07-19). "Inappropriate sinus tachycardia: an examination of existing definitions". EP Europace. 24 (10). Oxford University Press (OUP): 1655–1664. PMID 35851637.
- BENEZET-MAZUECOS, JUAN; RUBIO, JOSÉ M.; FARRÉ, JERÓNIMO; QUIÑONES, MIGUEL Á.; SANCHEZ-BORQUE, PEPA; MACÍA, ESTER (2013-03-19). "Long-Term Outcomes of Ivabradine in Inappropriate Sinus Tachycardia Patients: Appropriate Efficacy or Inappropriate Patients". Pacing and Clinical Electrophysiology. 36 (7). Wiley: 830–836. S2CID 33748387.
- Rodríguez-Mañero, Moisés; Kreidieh, Bahij; Al Rifai, Mahmoud; Ibarra-Cortez, Sergio; Schurmann, Paul; Álvarez, Paulino A.; Fernández-López, Xesús Alberte; García-Seara, Javier; Martínez-Sande, Luis; González-Juanatey, José Ramón; Valderrábano, Miguel (2017). "Ablation of Inappropriate Sinus Tachycardia". JACC: Clinical Electrophysiology. 3 (3). Elsevier BV: 253–265. PMID 29759520.
- Lee, Randall J.; Kalman, Jonathan M.; Fitzpatrick, Adam P.; Epstein, Laurence M.; Fisher, Westby G.; Olgin, Jeffrey E.; Lesh, Michael D.; Scheinman, Melvin M. (1995-11-15). "Radiofrequency Catheter Modification of the Sinus Node for "Inappropriate" Sinus Tachycardia". Circulation. 92 (10). Ovid Technologies (Wolters Kluwer Health): 2919–2928. PMID 7586260.