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| | '''For patient information, click [[Inappropriate sinus tachycardia (patient information)|here]]''' |
| {{Inappropriate sinus tachycardia}} | | {{Inappropriate sinus tachycardia}} |
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| {{SK}} IST; chronic nonparoxysmal sinus tachycardia | | {{SK}} IST; chronic nonparoxysmal sinus tachycardia |
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| ==Overview== | | == [[Inappropriate sinus tachycardia overview|Overview]] == |
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| ==Historical Perspective== | | == [[Inappropriate sinus tachycardia historical perspective|Historical Perspective]] == |
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| ==Pathophysiology== | | == [[Inappropriate sinus tachycardia pathophysiology|Pathophysiology]] == |
| The mechanism of the arrhythmia primarily involves the [[sinus node]] and peri-nodal tissue<ref>{{cite journal |doi=10.1054/jelc.2000.9648 |title=Electrophysiologic findings of a patient with inappropriate sinus tachycardia cured by selective radiofrequency catheter ablation |year=2000 |last1=Sato |first1=Toshiaki |last2=Mitamura |first2=Hideo |last3=Murata |first3=Mitsushige |last4=Shinagawa |first4=Kaori |last5=Miyoshi |first5=Shunichiro |last6=Kanki |first6=Hideaki |last7=Takatsuki |first7=Seiji |last8=Soejima |first8=Kyoko |last9=Miyazaki |first9=Toshihisa |journal=Journal of Electrocardiology |volume=33 |issue=4 |pages=381–6 |pmid=11099363}}</ref> and does not require the [[Atrioventricular node|AV node]] for maintenance. These patients have no apparent heart disease or other causes of sinus tachycardia. IST is thought to be due to abnormal autonomic control or [[dysautonomia]]. An autoimmune mechanism has been suggested as several studies have detected autoantibodies that activate beta adrenoreceptors in a portion of patients.<ref>{{cite journal |doi=10.1016/j.hrthm.2006.06.011 |title=Inappropriate sinus tachycardia may be related to an immunologic disorder involving cardiac β andrenergic receptors |year=2006 |last1=Chiale |first1=Pablo A. |last2=Garro |first2=Hugo A. |last3=Schmidberg |first3=Jorge |last4=Sánchez |first4=Rubén A. |last5=Acunzo |first5=Rafael S. |last6=Lago |first6=Manuel |last7=Levy |first7=Gabriela |last8=Levin |first8=Mariano |journal=Heart Rhythm |volume=3 |issue=10 |pages=1182–6 |pmid=17018348}}</ref><ref>{{cite journal |doi=10.1016/j.hrthm.2006.07.019 |title=Inappropriate sinus tachycardia and beta-receptor autoantibodies: A mechanistic breakthrough? |year=2006 |last1=Nattel |first1=Stanley |journal=Heart Rhythm |volume=3 |issue=10 |pages=1187–8 |pmid=17018349}}</ref>
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| ==Epidemiology and Demographics== | | == [[Inappropriate sinus tachycardia causes|Causes]] == |
| The disorder is uncommon.
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| ===Sex=== | | == [[Inappropriate sinus tachycardia differential diagnosis|Differentiating Inappropriate Sinus Tachycardia from other Diseases]] == |
| More common in women.
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| ===Age=== | | == [[Inappropriate sinus tachycardia epidemiology and demographics|Epidemiology and Demographics]] == |
| Most patients are in their late 20s to early 30s.
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| ==Differentiating Inappropriate Sinus Tachycardia from other Medical Conditions== | | == Diagnosis == |
| The following medical conditions must be excluded as a cause of tachycardia:
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| *[[Diabetes]]-induced [[autonomic dysfunction]]
| | [[Inappropriate sinus tachycardia diagnostic criteria|Diagnostic Criteria]] | [[Inappropriate sinus tachycardia history and symptoms|History and Symptoms]] | [[Inappropriate sinus tachycardia electrocardiogram|Electrocardiogram]] |
| *[[Hyperthyroidism]]
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| *[[Pheochromocytoma]]
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| *[[Substance abuse]]
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| ==Differentiating Inappropriate Sinus Tachycardia from other Supraventricular Arrhythmias==
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| ==Diagnosis==
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| ===Diagnostic Criteria===
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| No formal diagnostic criteria exist. A diagnosis of Inappropriate sinus tachycardia is primarily a diagnosis of exclusion and the following must be observed:
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| *Exclusion of all other causes of [[sinus tachycardia]]
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| *Common forms of [[supraventricular tachycardia]] (SVT) must be excluded
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| *Normal [[P wave]] morphology
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| *A resting [[sinus tachycardia]] is usually (but not always) present
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| *A nocturnal reduction in [[heart rate]] from over 100 beats per minute to 80 - 90 beats per minute
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| *There is an inappropriate [[heart rate]] response on exertion so that the heart rate accelerates to 140 - 150 beats per minute with minimal exertion.
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| *The mean [[heart rate]] during 24 hrs of monitoring is > 95 bpm
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| *Symptoms are documented to be due to [[tachycardia]]
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| *[[Hypotension]] may occasionally be observed
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| *[[Syncope]] ([[fainting]]) is occasionally reported
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| === Symptoms ===
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| Symptoms reported by patients vary in frequency and severity. Symptoms associated with Inappropriate sinus tachycardia include:
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| *[[Blurred vision]]
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| *Frequent [[palpitations]]
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| *[[Dyspnea]] ([[shortness of breath]]) and [[palpitations]] on exertion
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| *[[Pre-syncope]] (feeling as if about to [[faint]])
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| *[[Fatigue]]
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| *[[Dizziness]]
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| *[[Exercise intolerance]]
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| *Occasional [[paresthesia]] and [[cramping]]
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| *Symptoms associated with [[autonomic nervous system]] disturbance, including GI disturbance
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| *[[Orthostatic hypotension]] with a [[drop in blood pressure on standing]]
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| == Treatment == | | == Treatment == |
| Treatments in the form of [[pharmacological]] therapy or [[catheter ablation]] are available, although it is currently difficult to treat successfully.
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| ===Beta-blockers===
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| In so far as the pathophysiology of IST involves abnormal sensitivity to [[adrenaline]], [[betaa-blockers]] can be helpful.
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| ===Calcium Channel Blockers===
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| Although [[calcium channel blockers]] slow conduction through the [[AV node]], they have been marginally effective in the treatment of IST.
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| ===Ivabradine===
| | [[Inappropriate sinus tachycardia treatment guidelines|ACC/AHA/ESC Treatment Guidelines]] | [[Inappropriate sinus tachycardia medical therapy|Medical Therapy]] | [[Inappropriate sinus tachycardia surgery|Surgery]] |
| A new selective sinus node inhibitor [[Ivabradine]] is also being used to treat IST.
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| ===Treatments Related to Dysautonomia and POTS=== | | ==Case Studies== |
| In so far as the underlying pathophysiology may involve a [[dysautonomia]] and features of [[Postural orthostatic tachycardia syndrome]] ([[POTS]]), some therapies more commonly used to treat these disorders have been tried:
| | [[Inappropriate sinus tachycardia case study one|Case #1]] |
| ====[[Fludrocortisone]] ([[Florinef]])====
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| [[POTS]] and [[dysautonomia]] have been associated with decreases in blood volume, and this drug promotes sodium retention.
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| ====[[Midodrine]]====
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| Midodrine increases vasoconstriction, and prevents falls in blood pressure.
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| ====[[Serotonin-reuptake inhibitors]] ([[SSRI]]s)====
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| SSRIs have proven effective in treating some patients with [[dysautonomia]].
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| ===Catheter Ablation=== | | ==Related Chapters== |
| Invasive treatments include forms of [[Catheter ablation]] has gained favor among electrophysiologists in the treatment of IST.
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| ====Sinus Node Modification====
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| This procedure involves selective ablation of the [[sinus node]]. The rhythm reoccurs in 80% of cases.
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| ====Complete Sinus Node Ablation====
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| This procedure requires implantation of a Permanent [[Artificial pacemaker]])
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| ====AV Node Ablation====
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| In cases resistant to sinus node ablation, AV node ablation with creation of an [[iatrogenic]] [[complete heart block]], may be neccessary. This procedure requires implantation of a permanent [[artificial pacemaker]].
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| == See also ==
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| *[[Supraventricular tachycardia]] | | *[[Supraventricular tachycardia]] |
| *[[Sinus tachycardia]] | | *[[Sinus tachycardia]] |
| *[[Postural orthostatic tachycardia syndrome]] | | *[[Postural orthostatic tachycardia syndrome]] |
| *[[Dysautonomia]] | | *[[Dysautonomia]] |
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| ==References==
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| {{Reflist|2}}
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